A small room that serves as an entrance or waiting area leading to a larger or more important room.
From 'ante-' (before, in front of) from Latin, combined with 'room' from Old English 'rum' (space). This term has been used since at least the 17th century.
Anteroom tells you how space was organized by social hierarchy—you'd wait in this 'before-room' until granted access to the important person's chamber, literally architecture enforcing status!
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