enforce (v.)

word-forming element meaning "in; into," from French and Old French en-, from Latin in- "in, into" (from PIE root *en "in"). Typically assimilated before -p-, -b-, -m-, -l-, and -r-. Latin in- became en- in French, Spanish, Portuguese, but remained in- in Italian.

Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" (encircle), also "cause to be, make into" (endear), and used as an intensive (enclose). Spelling variants in French that were brought over into Middle English account for parallels such as ensure/insure, and most en- words in English had at one time or another a variant in in-, and vice versa.

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.