early 13c., "store room," from Anglo-French celer, Old French celier "cellar, underground passage" (12c., Modern French cellier), from Latin cellarium "pantry, storeroom," literally "group of cells;" which is either directly from cella (see cell), or from noun use of neuter of adjective cellarius "pertaining to a storeroom," from cella. The sense in late Middle English gradually shifted to "underground room." Cellar door attested by 1640s.