"Adair" is a Scottish name meaning "from the oak-ford". It was made a favorite due to the 18th century Scottish ballad: "Robert Adair".
I did, however, find one contradictory source which claims that "Adair" is a Scottish rendering of the Old English name "Edgar", meaning "prosperity + spear".
I guess will have to let our resident Scotsman, Daividh, settle this.
-- Nanaea