commando (n.) Look up commando at Dictionary.com
Afrikaans, "a troop under a commander," from Portuguese, literally "party commanded" (see command (v.)); in use c.1809 during the Peninsula campaign, then from 1834, in a South African sense, of military expeditions of the Boers against the natives; modern sense is from 1940 (originally shock troops to repel the threatened German invasion of England), first attested in writings of Winston Churchill, who could have picked it up during the Boer War. Phrase going commando "not wearing underwear" attested by 1996, U.S. slang, perhaps on notion of being ready for instant action.