Question: The Northumbrian Dialect was spoken in a kingdom whose name reflects what approximate southern limit to the kingdom's territory?

full_context: Document 1: Danish dialects: Danish dialects are the regional and local varieties of the Danish language. Danish dialects can be divided into the traditional dialects, which differ from modern Standard Danish in both phonology and grammar, and the Danish accents, which are local varieties of the Standard language distinguished mostly by pronunciation and local vocabulary colored by traditional dialects. Traditional dialects are now mostly extinct in Denmark, with only the oldest generations still speaking them. Danish traditional dialects are divided into three main dialect areas: Jutlandic dialect, Insular Danish and Bornholmian. Bornholmian is the only Eastern Danish dialect spoken in Denmark, since the other Eastern Danish dialects were spoken in areas ceded to Sweden and subsequently assimilated to Standard Swedish. Jutlandic is further divided into Southern Jutlandic and Northern Jutlandic, with Northern Jutlandic subdivided into North Jutlandic and West Jutlandic. Insular Danish is divided into Zealand, Funen, Møn and Lolland-Falster dialect areas - each with addition internal variation.
Document 2: Old Saxon: Old Saxon, also known as Old Low German, was a Germanic language and the earliest recorded form of Low German (spoken nowadays in Northern Germany, the northeastern Netherlands, southern Denmark, the Americas and parts of Eastern Europe). It is a West Germanic language, closely related to the Anglo-Frisian languages. It has been documented from the 8th century until the 12th century, when it gradually evolved into Middle Low German. It was spoken throughout modern northwestern Germany, primarily in the coastal regions and in the eastern Netherlands by Saxons, a Germanic tribe who inhabited the region of Saxony. It partially shares Anglo-Frisian's (Old Frisian, Old English) Ingvaeonic nasal spirant law which sets it apart from Low Franconian and Irminonic languages, such as Dutch, Luxembourgish and German.
Document 3: English language in Northern England: The English language in Northern England has been shaped by the region's history of settlement and migration, and today encompasses a group of related dialects known as Northern England English (or, simply, Northern English in the United Kingdom). Historically, the strongest influence on the varieties of the English language spoken in Northern England was the Northumbrian dialect of Old English, but contact with Old Norse during the Viking Age and with Irish English following the Great Famine have produced new and distinctive styles of speech. Some "Northern" traits can be found further south than others: only the northernmost accents of Northumberland and Tyneside retain the pre-Great Vowel Shift pronunciation of words such as "town" ( , ""toon""), but all northern accents lack the – split, and this trait extends a significant distance into the Midlands.
Document 4: Southumbrians: The Southumbrians or 'Suðanhymbre' were the Anglo-Saxon people occupying northern Mercia. The term might not have been used by the Mercians, and instead possibly coined by the Deiran or Bernician people as a territorial response to their own Kingdom of Northumbria. The "Anglo-Saxon Chronicle" refers to King Coenred as having become the King of the Southumbrians in 702, two years before he became King of all the Mercians. The fact that Coenred was the son of Wulfhere, the Mercian King, implies that Southumbria was a sub-kingdom of Mercia.
Document 5: Kings of the Angles: The Angles were a dominant Germanic tribe in the Anglo-Saxon settlement of Britain, and gave their name to the English, England and to the region of East Anglia. Originally from Angeln, present-day Schleswig-Holstein, a legendary list of their kings has been preserved in the heroic poems "Widsith" and "Beowulf", and the "Anglo-Saxon Chronicle".
Document 6: Yorkshire dialect: The Yorkshire dialect (also Broad Yorkshire or Tyke) is a Northern English language variety spoken in England's historic county of Yorkshire. The dialect has roots in older languages such as Old English and Old Norse. The Yorkshire Dialect Society exists to promote use of the dialect in both humour and in serious linguistics; there is also an East Riding Dialect Society.
Document 7: Music of Northumbria: Here Northumbria is taken to mean Northumberland, the northernmost county of England, and County Durham. This area, together with Tweeddale, was the ancient British tribal kingdom of Bernicia (Bryneich) and is notable for the stable ancestry of its present indigenous population, which has been identified by DNA analysis to be an offshoot of the group Scotland, Cumbria and the North of Ireland, but not so closely related to the other peoples of the UK. The area was the core of the outstanding artistic culture that developed during the Northumbrian Golden Age of the 7th and 8th centuries; it would be unwise to suggest that the area did not have a flourishing musical culture at that time, or that it was not of similar sophistication - Bede makes reference to the playing of the harp. The traditional music of this area may be a tangible legacy of the Bernicians - given that little is known of the antiquity of Northumbrian music; though traditional Northumbrian instruments would have had their limitations. However, much surviving early modern Northumbrian music is similar in form to the music of the Scottish Lowlands, so Northumberland's position on the cultural frontier between England and Scotland has played a significant role. The modern era has seen Northumbrian traditional music artificially pigeon holed into national divisions, into which Northumbrian music simply will not fit. Likewise, the crude assumption that the font of all music of substance was in the west and north of the British isles has undermined considered appreciation of the local repertoire.The region possesses a distinctive style of folk music with a strong and continuing tradition. The region is particularly noted for its tradition of border ballads, the Northumbrian smallpipe (a form of bagpipe unique to north-east England) and also a strong fiddle tradition in the region that was already well established in the 1690s. Northumbrian music is characterised by considerable influence from other regions (and vice versa), particularly southern Scotland and other parts of the north of England. Irish tunes are also much played in the region, as they are elsewhere. There has been a continuous tradition of traditional and distinctive Northumbrian styles since the 18th century – there have also been 'revivals' in the late nineteenth century and again in the mid-twentieth. More recently, Northumbrian folk music, and particularly the use of the Northumbrian pipes, has become one of the liveliest and most widely known forms of folk music in Britain.
Document 8: Northumbrian dialect: Northumbrian was a dialect of Old English spoken in the Anglian Kingdom of Northumbria. Together with Mercian, Kentish and West Saxon, it forms one of the sub-categories of Old English devised and employed by modern scholars.
Document 9: Earl of Northumbria: Earl of Northumbria was a title in the Anglo-Danish, late Anglo-Saxon, and early Anglo-Norman period in England. The earldom of Northumbria was the successor of the earldom of Bamburgh. In the seventh century, the Anglo-Saxon kingdoms of Bernicia and Deira were united in the kingdom of Northumbria, but this was destroyed by the Vikings in 867. Southern Northumbria, the former Deira, then became the Viking kingdom of York, while English earls ruled the former northern kingdom of Bernicia from their base at Bamburgh. The northern part of Bernicia was lost to the Scots, probably in the late tenth century. In 1006 Uhtred the Bold was earl of Bamburgh, and Æthelred the Unready appointed him earl of York as well, re-uniting the area of Northumbria still under English control into a single earldom. Uhtred was murdered in 1016, and Cnut then appointed Eric of Hlathir earl of Northumbria at York, but Uhtred's dynasty held onto Bernicia until 1041, when the earldom was again united. A descendant of Uhtred, Gospatric, was appointed earl by William the Conqueror in 1067, but William expelled him in 1072. Gospatric was then given lands in Scotland, and his descendants became earls of Dunbar. The earldom of Northumbria was broken up in the early Norman period and dissolved into the earldoms of York and Northumberland, with much land going to the prince-bishopric of Durham.
Document 10: English of Northumbria: The Northumbrian language or Northumbria English is an English language or dialect of English (""Northumbrian Language"" may only refer to the broadly spoken Northumbrian whereas Northumbrian English may just refer to the Standard English as spoken in Northumbria and featuring various Northumbrian words and forms), and a variant of Northern English with the Geordie dialect being one of the subsets of Northumbrian the others being Northern (north of the River Coquet), Western (from Allendale through Hexham up to Kielder), Southern or Pitmatic (the mining towns such as Ashington and much of Durham) Mackem (Wearside), Smoggie (Teesside) and possibly also Tyke (Yorkshire). It is spoken mainly if not exclusively in the modern day counties of Northumberland and Durham. Whilst all sharing similarities to the more famous Geordie dialect and most of the time not distinguishable by non-native speakers, there are a few differences between said dialects not only between them and Geordie but also each other.
Document 11: Kingdom of Strathclyde: Strathclyde (lit. "Strath of the River Clyde"), originally Cumbric: Ystrad Clud or Alclud (and Strath-Clota in Anglo-Saxon), was one of the early medieval kingdoms of the Britons in "Hen Ogledd" ("the Old North"), the Brythonic-speaking parts of what is now southern Scotland and northern England. The kingdom developed during the post-Roman period. It is also known as Alt Clut, a Brittonic term for Dumbarton Castle, the medieval capital of the region. It may have had its origins with the Brythonic Damnonii people of Ptolemy's "Geography".
Document 12: English language: English is a West Germanic language that was first spoken in early medieval England and is now a global "lingua franca". Named after the Angles, one of the Germanic tribes that migrated to England, it ultimately derives its name from the Anglia (Angeln) peninsula in the Baltic Sea. It is closely related to the Frisian languages, but its vocabulary has been significantly influenced by other Germanic languages, particularly Norse (a North Germanic language), as well as by Latin and Romance languages, particularly French.
Document 13: Kingdom of Northumbria: The Kingdom of Northumbria ( ; Old English: "Norþhymbra rīce" , "kingdom of the Northumbrians") was a medieval Anglian kingdom in what is now northern England and south-east Scotland, which subsequently became an earldom in a unified English kingdom. The name reflects the approximate southern limit to the kingdom's territory, the Humber estuary.
Document 14: Rheged: Rheged (] ) was one of the kingdoms of the "Hen Ogledd" ("Old North"), the Brittonic-speaking region of what is now Northern England and southern Scotland, during the post-Roman era and Early Middle Ages. It is recorded in several poetic and bardic sources, although its borders are not described in any of them. Some modern scholars have suggested that it included what is now Cumbria in North West England and possibly extended into Lancashire and Scotland. In some sources, Rheged is intimately associated with the king Urien Rheged and his family. Its inhabitants spoke Cumbric, a Brittonic dialect closely related to Old Welsh.
Document 15: Hen Ogledd: Yr Hen Ogledd (] ), in English the Old North, is the region of Northern England and the southern Scottish Lowlands inhabited by the Celtic Britons of sub-Roman Britain and the Early Middle Ages. Its denizens spoke a variety of the Brittonic language known as Cumbric. The Hen Ogledd was distinct from the parts of northern Britain inhabited by the Picts, Anglo-Saxons, and Scoti as well as from Wales, although the people of the Hen Ogledd were the same Brittonic stock as the Picts, Welsh and Cornish, and the region loomed large in Welsh literature and tradition for centuries after its kingdoms had disappeared.
ground_truth: the Humber estuary