force

1250–1300; (noun) Middle English < Middle French < Vulgar Latin *fortia, derivative of Latin fortis strong; (v.) Middle English forcen < Anglo-French, Old French forcer, derivative of the noun

3. See strength.

Force has a straightforward, uncomplicated history: the word comes via Old French force from fortia, an unattested Vulgar Latin feminine singular noun from Latin fortia, a neuter plural adjective used as a noun, and derived from the adjective fortis “strong, robust, brave.” Nouns and adjectives that were originally neuter in Latin usually become masculine in Romance (languages descended from Latin): corpus “body,” neuter in Latin, becomes corps in French, corpo in Italian, and cuerpo in Spanish, all masculine nouns. The notable exception is that many Latin neuter plural adjectives and participles ending in -ia become feminine singular nouns in Romance because these neuter plurals end in -a, which looks like the singular of Latin feminine nouns of the first declension, especially if the new noun has an abstract or collective meaning. So appārentia, the neuter plural of Latin appārēns “apparent,” will become apparence in French, apparenza in Italian, apariencia in Spanish, aparança in Catalan, and aparenţă in Romanian; and fortia will become force in French, forza in Italian, fuerza in Spanish, força in Catalan, and forţă in Romanian.