casual, generic term of address for a man, 1928, from Irish and Gaelic mac, a common element in Scottish and Irish names (literally "son of;" see Mac-); hence used generally from 1650s for "a Celtic Irishman."

common conjoined prefix in Scottish and Irish names, from Old Celtic *makko-s "son." Cognate *makwos "son" produced Old Welsh map, Welsh mab, ap "son;" also probably cognate with Old English mago "son, attendant, servant," Old Norse mögr "son," Gothic magus "boy, servant," Old English mægð "maid" (see maiden).

Formerly often abbreviated to M' and followed by a capital letter, or spelled out Mac and then rarely used with a capital; as, M'Donald, Macdonald, McDonald.

trademark name (McDonald's Corp.) of a type of large hamburger sandwich; by 1968.

by 1992, vaguely from Federal Home Loan Mortgage Corporation.

patronymic element in Welsh pedigrees and names, earlier map "son," cognate with Gaelic mac. Since 17c. merged into surnames and reduced to P- or B- (Ap Rhys = Price, Ap Evan = Bevan, Bowen = Ap Owen, etc.).

It is said that a Welshman who evidently was not willing to be surpassed in length of pedigree, when making out his genealogical tree, wrote near the middle of his long array of 'aps' — "about this time Adam was born." ["Origin and Significance of our Names," The Chautauquan, Oct. 1887-July 1888]

Gaelic Mac Dhuibh "son of Dubh," literally "black."

Irish surname, from Gaelic Mac Mhaolain "son of the tonsured one."

Irish surname, from Gaelic Mac Pharlain "son of Parlan," from Old Irish Parthalon "Bartholomew."

Irish surname, from Gaelic Mac Shuibhne "son of Suibhne," literally "pleasant."

Irish surname, from Irish mac "son of" + Conall, from Celtic kunovalos "high-powerful."