Question: What does the name of the first castle erected in 13th century, means what in Gaelic?

Context paragraphs:
Classical Gaelic: Classical Gaelic (Scottish Gaelic: "Gàidhlig Chlasaigeach" ; Irish: "Gaeilge Chlasaiceach" ) was the shared literary form that was in use in Scotland and Ireland from the 13th to the 18th centuries.  The language may be thought of as a high-register version of Early Modern Irish.  Although the first written signs of Scottish Gaelic having diverged from Irish appear as far back as the 12th century annotations of the Book of Deer, Scottish Gaelic did not have a standardised form and did not appear in print on a significant scale until the 1767 translation of the New Testament into Scottish Gaelic—though John Carswell's "Foirm na n-Urrnuidheadh ", an adaptation of John Knox's "Book of Common Order", was the first book printed in either Scottish or Irish Gaelic.

Cilgerran Castle: Cilgerran Castle (Welsh: "Castell Cilgerran" ) is a 13th-century ruined castle located in Cilgerran, Pembrokeshire, Wales, near Cardigan.  The first castle on the site was thought to be built by Gerald of Windsor around 1110–1115, and it changed hands several times over the following century between English and Welsh forces.  In the hands of William Marshal, 2nd Earl of Pembroke, the construction of the stone castle began after 1223.  After passing through successive families, it was left to ruin and eventually abandoned by 1400.  The castle backs onto a cliff face, with the remaining ruins dating from the 13th century.  It was most heavily fortified where it faces inland, and includes a pair of drum towers rather than a central keep which remain.  It passed into the hands of the National Trust in 1938, who open it to the public.

Allington Castle: Allington Castle is a stone-built moated castle in Allington, Kent, just north of Maidstone, in England.  The first castle on the site was an unauthorised fortification, built during The Anarchy of the early 12th century and torn down later in the century when royal control was reasserted.  It was replaced by a manor house, which was fortified with royal permission in the 13th century.  Various alterations and expansions were made by successive owners over the following two centuries.  The property was developed into a fortified compound with six towers at irregular intervals along the curtain wall and domestic buildings in the interior, including one of the first long galleries built in England.  In 1554 it was seized by the Crown in the course of dispossessing its owner, Sir Thomas Wyatt the Younger, after the failure of his rebellion against Queen Mary.

Douglas (surname): Douglas (occasionally spelled "Douglass") is a common surname of Scottish origin, thought to derive from the Gaelic "dubh glas", meaning "black stream".  There are numerous places in Scotland from which the surname is derived.  The surname has developed into the given name "Douglas".  "Douglas" is a habitational name, which could be derived from any of the many places so-named.  While there are numerous places with this name in Scotland, it is thought, in most cases, to refer to Douglas, South Lanarkshire, the location of Douglas Castle, the chief stronghold of the Lords of Douglas.  The Scottish Gaelic form of the given name is "Dùbhghlas"; the Irish language form it is "Dúghlas", and "Dubhghlas", which are pronounced ] .  According to George Fraser Black, in southern Argyllshire the surname is an Anglicised form of the surnames "MacLucas", "MacLugash" (which are derived from the Gaelic "Mac Lùcais").

Torthorwald Castle: Torthorwald Castle is a large ruined rectangular tower at the center of the village of Torthorwald just outside Dumfries in south west Scotland.  The first castle on the site was an earthwork motte-and-bailey built in the 12th century.  The earliest building which forms part of the current ruins was built in the 14th century.

Cardiff Castle: Cardiff Castle (Welsh: "Castell Caerdydd" ) is a medieval castle and Victorian Gothic revival mansion located in the city centre of Cardiff, Wales.  The original motte and bailey castle was built in the late 11th century by Norman invaders on top of a 3rd-century Roman fort.  The castle was commissioned either by William the Conqueror or by Robert Fitzhamon, and formed the heart of the medieval town of Cardiff and the Marcher Lord territory of Glamorgan.  In the 12th century the castle began to be rebuilt in stone, probably by Robert of Gloucester, with a shell keep and substantial defensive walls being erected.  Further work was conducted by Richard de Clare, 6th Earl of Gloucester, in the second half of the 13th century.  Cardiff Castle was repeatedly involved in the conflicts between the Anglo-Normans and the Welsh, being attacked several times in the 12th century, and stormed in 1404 during the revolt of Owain Glyndŵr.

Caerlaverock Castle: Caerlaverock Castle (from "caer laverock", "lark castle") is a moated triangular castle first built in the 13th century.  It is located on the southern coast of Scotland, 11 km south of Dumfries, on the edge of the Caerlaverock National Nature Reserve.  Caerlaverock was a stronghold of the Maxwell family from the 13th century until the 17th century when the castle was abandoned.  It was besieged by the English during the Wars of Scottish Independence, and underwent several partial demolitions and reconstructions over the 14th and 15th centuries.  In the 17th century, the Maxwells were created Earls of Nithsdale, and built a new lodging within the walls, described as among "the most ambitious early classical domestic architecture in Scotland".  In 1640 the castle was besieged for the last time and was subsequently abandoned.  Although demolished and rebuilt several times, the castle retains the distinctive triangular plan first laid out in the 13th century.  Caerlaverock Castle was built to control trade in early times.

Thetford Castle: Thetford Castle is a medieval motte and bailey castle in the market town of Thetford in the Breckland area of Norfolk, England.  The first castle in Thetford, a probable 11th century Norman ringwork called Red Castle, was replaced in the 12th century by a much larger motte and bailey castle on the other side of the town.  This new castle was largely destroyed in 1173 by Henry II, although the huge motte, the second largest man-made mound in England, remained intact.  The motte, recognised as a scheduled monument, now forms part of a local park, and the remains are known variously as Castle Hill, Castle Mound and Military Parade.

Douglas Castle: Douglas Castle was a stronghold of the Douglas family from medieval times to the 20th century.  The first castle, erected in the 13th century, was destroyed and replaced several times until the 18th century when a large mansion house was built in its place.  This too was demolished in 1938, and today only a single corner tower of the 17th-century castle remains.  The castle was the former family seat of the Prime Minister, Sir Alec Douglas-Home.  The castle was located around 1 km north-east of the village of Douglas, South Lanarkshire, in south-west Scotland.  The remains are protected as a category C listed building.

Balloch Castle: Balloch Castle is an early 19th-century country house situated at the southern tip of Loch Lomond, in West Dunbartonshire, Scotland.  Balloch was a property of the Lennox family from the 11th century, and the old castle was built in the 13th century.  In the 19th century the estate was purchased by John Buchanan of Ardoch, who demolished the ruins of the old castle and erected the present building.  The Tudor Gothic architecture is the work of Robert Lugar.  In 1915 Balloch was bought by Glasgow City Corporation, and has been leased by West Dunbartonshire Council since 1975.  The estate was designated as a country park in 1980, and since 2002 has been part of Loch Lomond and The Trossachs National Park.  Although the house has been periodically used for visitor facilities and council offices, it is now included on the Buildings at Risk Register.  Balloch Castle is a category A listed building, and the estate is included on the Inventory of Gardens and Designed Landscapes in Scotland.

Supporting paragraphs: Douglas (surname) Douglas Castle
Answer: "dubh glas", meaning "black stream"