'ballroom' is a compound from English 'ball' + 'room'. 'ball' (meaning a formal dance) comes from Old French 'bal' (from Late Latin/Italian roots related to 'ballare' meaning 'to dance'), and 'room' comes from Old English 'rūm' meaning 'space' or 'room'.

'ball' entered Middle English from Old French 'bal' (itself from Latin/Italian words related to dancing), and combined with Old English 'rūm' to form the compound 'ballroom' in Early Modern English to denote a room for dances; this compound has remained in use to modern English.

Initially and historically it referred specifically to a room used for balls (formal dances); over time the meaning broadened slightly to include large rooms used for a variety of formal social events (banquets, receptions) as well as dancing.