"money," 1520s, from German and Dutch gelt "gold, money," from Proto-Germanic *geldam "payment" (see geld (n.)). In some later uses from Yiddish gelt, from Old High German gelt "payment, reward," from the same source.
gelt (adj.)
past participle of geld (v.); hence, as an adjective, "castrated" (mid-15c.).