underhanded (adj.)youdaoicibaDictYouDict[underhanded 词源字典]
in reference to a throw, etc., "performed or done with the knuckles turned under," 1807, from under + hand (n.). Compare underhand. As "in secret," from 1825; as "with too few people," from 1834. Related: Underhandedly; underhandedness.[underhanded etymology, underhanded origin, 英语词源]