Mac-

Old English mægden, mæden "unmarried woman (usually young); virgin; girl; maidservant," diminutive of mægð, mægeð "virgin, girl; woman, wife," from Proto-Germanic *magadin- "young womanhood, sexually inexperienced female" (source also of Old Saxon magath, Old Frisian maged, Old High German magad "virgin, maid," German Magd "maid, maidservant," German Mädchen "girl, maid," from Mägdchen "little maid"), fem. variant of PIE root *maghu- "youngster of either sex, unmarried person" (source also of Old English magu "child, son, male descendant," Avestan magava- "unmarried," Old Irish maug "slave").

Also in Middle English "a man lacking or abstaining from sexual experience" (c. 1200). As the name of a guillotine-like instrument of execution by beheading, from 1580s.

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."