Entries linking totour de force force(n.) c. 1300, "physical strength," from Old Frenchforce"force, strength; courage, fortitude; violence, power, compulsion" (12c.), from Vulgar Latin*fortia(source also of Old Spanishforzo, Spanishfuerza, Italianforza), noun use of neuter plural of Latin...
Latin, literally "in fact, in reality," thus, "existing, but not necessarily legally ordained or morally right;" from facto, ablative of factum "deed, act" (see de + fact). Entries linking to de facto de Latin adverb and preposition of separation in space, meaning "down from, off, ...