Old English stigrap, literally "climbing rope," from stige "a climbing, ascent" (from Proto-Germanic *stigaz "climbing;" see stair) + rap (see rope). Originally a looped rope as a help for mounting. Germanic cognates include Old Norse stigreip, Old High German stegareif, German stegreif. Surgical device used in childbirth, etc., so called from 1884. Stirrup-cup (1680s) was a cup of wine or other drink handed to a man already on horseback and setting out on a journey, hence "a parting glass" (cf. French le vin de l'etrier).
stirrup stir·rup (stûr'əp, stĭr'-)