c.1300, "physical strength," from Old French force (12c.) "force, strength, courage, fortitude; violence, power, compulsion," from Vulgar Latin *fortia (cf. Spanish fuerza, Italian forza), noun use of neuter plural of Latin fortis "strong" (see fort). Meaning "body of armed men, army" first recorded late 14c. (also in Old French). Physics sense is from 1660s; force field attested by 1920.