schm-youdaoicibaDictYouDict[schm- 词源字典]
substituted for the initial sound of a word and reduplicated with it to convey derision (as in "Oedipus schmoedipus" in the punchline of the old joke about the Jewish mother and the psychiatrist), 1929, from the numerous Yiddish words that begin with this sound.[schm- etymology, schm- origin, 英语词源]
tagline (n.)youdaoicibaDictYouDict
"punchline of a joke," 1926, originally "last line in an actor's speech" (1916), from tag (n.1) + line (n.).