mansion n.

mid-14c., "chief residence of a lord," from Old French mansion "stay, permanent abode, house, habitation, home; mansion; state, situation" (13c.), from Latin mansionem (nominative mansio) "a staying, a remaining, night quarters, station," noun of action from past participle stem of manere "to stay, abide" (from PIE root *men- (3) "to remain"). Sense of "any large and stately house" is from 1510s. The word also was used in Middle English as "a stop or stage of a journey," hence probably astrological sense "temporary home" (late 14c.).