Quotation from Burke's Peerage of Great Britain:
"The surname of Ker or Car is of great antiquity in Scotland and some are of the opinion that they came originally to this Island from France, where there are several considerable families who made a great figure even before the 10th century and whose posterity are subsisting in that knigdom to this day. That one of these, a man of rank and spirit came over to England with William the Conqueror in 1066, had a considerable command in his army and having remarkably distinguished himself for courage and conduct, gat from that great Prince a large share of the conquered lands, particularly in the North of England, where his posterity still subsists and that of him all the Kers in Great Britain are descended. Several families of that name lived during the time of Alexander III (1249)."