c. 1300, "physical strength," from Old French force "force, strength; courage, fortitude; violence, power, compulsion" (12c.), from Vulgar Latin *fortia (source also of Old Spanish forzo, Spanish fuerza, Italian forza), noun use of neuter plural of Latin fortis "strong, mighty; firm, steadfast; brave, bold" (see fort).
Meanings "power to convince the mind" and "power exerted against will or consent" are from mid-14c. Meaning "body of armed men, a military organization" first recorded late 14c. (also in Old French). Physics sense is from 1660s; force field attested by 1920. Related: Forces.
c. 1300, forcen, also forsen, "exert force upon (an adversary)," from Old French forcer "conquer by violence," from force "strength, power, compulsion" (see force (n.)). From early 14c. as "to violate (a woman), to rape." From c. 1400 as "compel by force, constrain (someone to do something)." Meaning "bring about by unusual effort" is from 1550s. Card-playing sense is from 1746 (whist). Related: Forced; forcing.