Question: What is the river 3 mi north-west of Gainsborough said to take its name from?

full_context: Document 1: Trent Aegir: The Trent Aegir, also known as the Eagre, is a tidal bore on the River Trent in England. At certain times of the year, the lower tidal reaches of the Trent experience a moderately large bore (up to five feet (1.5m) high). It is said to take its name from "Ægir", the Norse god of the ocean, although this is disputed.
Document 2: Oceanus: Oceanus ( ; Greek: Ὠκεανός "Ōkeanós", ] ), also known as Ogenus ("Ogenos", Ωγηνος) or Ogen (Ωγην), was a divine figure in classical antiquity, believed by the ancient Greeks and Romans to be the divine personification of the sea, an enormous river encircling the world.
Document 3: West Stockwith: West Stockwith is a village within the Bassetlaw district of Nottinghamshire, England. The population at the 2011 census was 327. it lies on the west bank of the River Trent, 3 mi north-west of Gainsborough and 1.5 mi east of Misterton. West Stockwith is an ecclesiastical parish in the Church of England Diocese of Southwell and Nottingham with the parish church of St Mary the Virgin's Church, West Stockwith being built in 1722.
Document 4: Story (surname): The surname Story (and its variant spelling Storey) originates from the Old Norse personal epithet “Stóri”, a derivative of “Storr” which means “large” or “big”. Even though it has been established that the root of the name is “Storr”, R.E.K. Rigbeye, in his book "The Storey’s of Old" claims that the suffix “ey[e]”, in the variant of Storey, is equivalent to the Icelandic “ig” and signifies “water”. According to him, “Storr” also denotes large in the sense of vast and rough. Rigbeye’s assumption therefore, is that “Storey” means "dweller by large and rough water". This may be explained by the Norse affinity to sea exploration, or the fact that the first Storys settled near the Lake District, and so the name might refer to the habitation which they chose. The earliest Norse settlement of which the first Storys would have been a part, took place in the 9th century north of Carlisle near the Solway Firth. This area then known as Strathclyde, was situated in the northwestern part of England, along the Scottish border. The earliest Storys would have settled on the English side of the border, most likely in the plains along the river Eden. The English or Anglo-Saxon population, among whom the Norse settled, spoke a similar language but pronounced many words in a different way. So, “Storr” among the Norse would have been enunciated as “Styr” in English.
Document 5: East Stockwith: East Stockwith is a village within the civil parish of East Stockwith, in the West Lindsey district of Lincolnshire, England. It lies on the River Trent, 3 mi north-west of Gainsborough. The River Trent Aegir, a tidal bore, reaches the village. In 2001 it had a total resident population of 209, increasing to 314 at the 2011 census.
Document 6: Horkstow: Horkstow is a village and civil parish in North Lincolnshire, England, 4 mi south-west from Barton-Upon-Humber, 1 mi south from South Ferriby and 9 mi north from Brigg. It lies on the B1204, and 1 mi east from the navigable River Ancholme. It is one of the five "Low Villages" - Worlaby, Bonby, Saxby All Saints, Horkstow and South Ferriby - between Brigg and the River Humber, so-called because of their position below the northern edge of the Lincolnshire Wolds. Horkstow was previously part of South Humberside administrative district, and before that, the North Lindsey division of Lindsey, Lincolnshire.
Document 7: Ruskington: Ruskington is a large village and civil parish in the North Kesteven district of Lincolnshire, England, located on the north-south B1188 road and slightly north of the A153 road. The village contains approximately 2,200 dwellings and is approximately 1 mi in length, measured from east to west. The population of the civil parish was 5,169 at the 2001 census, increasing to 5,637 at the 2011 census.
Document 8: Neshmet: The Neshmet bark was a vessel belonging to the god Nun. The ancient Egyptian deity Osiris was transported in it on the river Nile during the Osiris festival at Abydos. The god's departure from his temple, journey to his tomb, and triumphant return were enacted and drew many spectators who participated in the public parts of the mysteries.
Document 9: River Thames: The River Thames ( ) is a river that flows through southern England, most notably through London. At 215 mi , it is the longest river entirely in England and the second longest in the United Kingdom, after the River Severn. It also flows through Oxford (where it is called Isis), Reading, Henley-on-Thames and Windsor. The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock. It rises at Thames Head in Gloucestershire, and flows into the North Sea via the Thames Estuary. The Thames drains the whole of Greater London.
Document 10: Besthorpe, Nottinghamshire: Besthorpe is a small village in north-east Nottinghamshire close to the border with Lincolnshire. It is a Civil Parish in the Newark & Sherwood district of Nottinghamshire. The population of the civil parish as of the 2011 census is 195. The village is on the A1133 between Newark and Gainsborough, and is 1.5 miles north of the larger village of Collingham, North East of Newark on Trent. The village lies 1 mile east of the River Trent and the River Fleet flows South to East parallel with the village & A1133. Besthorpe acquired Conservation Village status in 2006 because it has maintained much of its original layout focused on Low Road and the Green.
Document 11: Turgai Sea: The Turgai (or Turgay) Sea or Turgai Strait, also known as the West Siberian Sea, was a large shallow body of salt water (an epicontinental or epeiric sea) of the Mesozoic and Cenozoic Eras. It extended north of the present-day Caspian Sea to the "paleo-Arctic" region, and was in existence from Middle Jurassic to Oligocene times, from approximately 160 to 29 million years ago.
Document 12: 13 Egeria: 13 Egeria is a large main-belt G-type asteroid. It was discovered by Annibale de Gasparis on November 2, 1850. Egeria was named by Urbain Le Verrier, whose computations led to the discovery of Neptune, after the mythological nymph Egeria of Aricia, Italy, the wife of Numa Pompilius, second king of Rome.
Document 13: Tír na nÓg: In Irish mythology and folklore, Tír na nÓg (] ; "Land of the Young") or Tír na hÓige ("Land of Youth") is one of the names for the Otherworld, or perhaps for a part of it. It is depicted as a supernatural realm of everlasting youth, beauty, health, abundance and joy. Its inhabitants are the Tuatha Dé Danann, the gods of pre-Christian Ireland. In the "echtrae" (adventure) and "immram" (voyage) tales, various Irish mythical heroes visit Tír na nÓg after a voyage or an invitation from one of its residents. They reach it by entering ancient burial mounds or caves, or by going under water or across the sea.
Document 14: Susworth: Susworth is a hamlet in the West Lindsey district of Lincolnshire, England. It is situated on the east bank of the River Trent, 3 mi west from Scotter, in which civil parish it lies. The nearest large towns are Gainsborough, approximately 7 mi to the south, and Scunthorpe 7 miles to the north-east.
Document 15: North Scarle: North Scarle is a village and civil parish in the North Kesteven district of Lincolnshire, England. The population of the civil parish at the 2011 census was 640. The village is situated on the River Trent, about 8 mi south-west from the city and county town of Lincoln, and on the county boundary with Nottinghamshire.
ground_truth: the Norse god of the ocean