lit- + -u, probably of the same origin as litistää, litteä (compare litussa, littuun); the ungeminated -t- instead of -tt- may be influence from litukka or lituska, or even itu (“sprout”). The word was given its current botanical sense by Finnish physician and philologist Elias Lönnrot in his Flora Fennica from 1860, prior to which the word mainly meant "thin, semi-ripe (pea) pod".