gambit n.

"chess opening in which a pawn or piece is risked for advantage later," 1650s, gambett, from Italian gambetto, literally "a tripping up" (as a trick in wrestling), from gamba "leg," from Late Latin gamba "horse's hock or leg" (see gambol (n.)).

Applied to chess openings in Spanish in 1561 by Ruy Lopez, who traced it to the Italian word, but the form in Spanish generally was gambito, which led to French gambit, which has influenced the English spelling of the word. The broader sense of "opening move meant to gain advantage" in English is recorded from 1855.