mansion (n.) Look up mansion at Dictionary.com
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 *men- "to remain, wait for" (cognates: Greek menein "to remain," Persian mandan "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.).