means A large, imposing, and often grand residence, the kind with more rooms than a single family could reasonably occupy.

from From Latin 'mansio,' meaning a 'staying' or 'dwelling' — literally a place where one remains, from the verb 'manere,' to stay or abide. The same root that gives us 'permanent' and 'remain.' It traveled through Old French 'mansion' (a dwelling, a stopping place) into English, where over the centuries the humble idea of 'a place to stay' swelled, room by room, into the sprawling grandeur we picture today.