The term "Blair" is the genitive of a gaelic word, "Blar" meaning "field" or "battle field".
It is used widely for both places and surnames, one of the earliest known for the former being the Barony of Blair in Ayrshiregranted by King William in the mid-12th century.
Association with Sir William Wallace
Sir Bryce Blair was an adherent of Sir William Wallace but was executed by the English at the Barns of Ayr in 1296.
His brother's son, Roger, was knighted by King Robert the Bruce for his services before & at Bannockburn.
Blair House at Dalry, Ayrshire was occupied continuously by the family between 1202 and 1980.
Blair Castle, Blair Atholl, Pitlochry, UK (Modern)
The earliest known part of the present castle dates from 1269 and is known as Comyn’s Tower.The original tower had an extension added to it by the 3rd Earl in 1530 to form a Great Hall (the present Dining Room) over a series of vaulted chambers below.