where heard: likely first in my pre-socratics class, or maybe before... recently, in Durrell's Justine and in the movie Mysterious Skin...
what it means: well now...
1593, from L. Catamitus, corruption of Ganymedes, the beloved cup-bearer of Jupiter.
"worthless person" (especially a young hoodlum), 1917, probably from punk kid "criminal's apprentice," underworld slang first attested 1904 (with overtones of "catamite"). Ultimately from punk "prostitute, harlot, strumpet," first recorded 1596, of unknown origin. For sense shift from "harlot" to "homosexual," cf. gay. By 1923 used generally for "young boy, inexperienced person" (originally in show business, e.g. punk day, circus slang from 1930, "day when children are admitted free"). The verb meaning "to back out of" is from 1920. The "young criminal" sense is no doubt the inspiration in punk rock first attested 1971 (in a Dave Marsh article in "Creem"), popularized 1976.
1914, Amer. Eng., from hobo slang, "a catamite;" specifically "a young male kept as a sexual companion, esp. by an older tramp," from Yiddish genzel, from Ger. Gänslein "gosling, young goose." The secondary, non-sexual meaning "young hoodlum" seems to be entirely traceable to Dashiell Hammett, who snuck it into "The Maltese Falcon" (1939) while warring with his editor over the book's racy language.
" 'Another thing,' Spade repeated, glaring at the boy: 'Keep that gunsel away from me while you're making up your mind. I'll kill him.' " The context implies some connection with gun and a sense of "gunman," and evidently the editor bought it. The word was retained in the script of the 1941 movie made from the book, so evidently the Motion Picture Production Code censors didn't know it either.
"The relationship between Kasper Gutman (Sidney Greenstreet) and his young hit-man companion, Wilmer Cook (Elisha Cook, Jr.), is made fairly clear in the movie, but the overt mention of sexual perversion would have been deleted if the censors hadn't made the same mistaken assumption as Hammett's editor." [Hugh Rawson, "Wicked Words," 1989, p.184]