Scotland in the Early Middle Ages to be adopted for house building, often combining layers of stone with turf. Place-name evidence, particularly the use of the prefix "pit", meaning land or a field, suggests that the heaviest areas of Pictish settlement were in modern Fife, Perthshire, Angus, Aberdeen and around the Moray Firth, although later Gaelic migration may have erased some Pictish names from the record. Early Gaelic settlement appears to have been in the regions of the western mainland of Scotland between Cowal and Ardnamurchan, and the adjacent islands, later extending up the West coast in the 8th century. There is place name and archaeological
Firth "firth" (e.g. the Minch and Loch Torridon); instead, these are often called sea lochs. Before about 1850, the spelling "Frith" was more common. A firth is generally the result of ice age glaciation and is very often associated with a large river, where erosion caused by the tidal effects of incoming sea water passing upriver has widened the riverbed into an estuary. Demarcation can be rather vague. The Firth of Clyde is sometimes thought to include the estuary as far upriver as Dumbarton, but the Ordnance Survey map shows the change from river to firth occurring off Port Glasgow, while