hanger (n.)youdaoicibaDictYouDict[hanger 词源字典]
early 15c., "one who hangs (something)," especially "executioner," later also "one who chooses pictures for an exhibition;" agent noun from hang (v.). Meaning "something that is suspended" is late 15c. Meaning "thing from which something is hung" is from 1690s. Meaning "loop or strap in a garment for hanging on a peg" is from 1680s; of wood or wire coat or dress hangers from 1873. Hanger-on is from 1540s.[hanger etymology, hanger origin, 英语词源]
parasite (n.)youdaoicibaDictYouDict
1530s, "a hanger-on, a toady, person who lives on others," from Middle French parasite (16c.) or directly from Latin parasitus "toady, sponger," and directly from Greek parasitos "one who lives at another's expense, person who eats at the table of another," from noun use of an adjective meaning "feeding beside," from para- "beside" (see para- (1)) + sitos "food," of unknown origin. Scientific meaning "animal or plant that lives on others" is first recorded 1640s (implied in parasitical).