Shm-reduplication is a form of reduplication in which the original word or its first syllable (the base) is repeated with the copy (the reduplicant) beginning with shm- (sometimes schm-), pronounced //. The construction is generally used to indicate irony, derision or skepticism with respect to comments about the discussed object:
- He's just a baby!
- "Baby-shmaby". He's already 5 years old!
- What a sale!
- "Sale, schmale". I'm waiting for a larger discount.
- "Whenever we go to a fancy-schmancy restaurant, we feel like James Bond."
The reduplicated combination belongs to the same syntactical category as the original.
- Words beginning with a single consonant typically replace that consonant with shm- (table shmable).
- Words beginning with a consonant cluster are more variable: some speakers replace only the first consonant if possible (breakfast shmreakfast), others replace the entire cluster (breakfast shmeakfast).
- Vowel-initial words prepend the shm- directly to the beginning of the reduplicant (apple shmapple).
- Some speakers target the stressed syllable rather than the first syllable (incredible inshmedible); a subset of these do not copy base material preceding the stressed syllable (incredible shmedible; cf. Spitzer 1952).
- When speaking two words, usually only the second word is shm-reduplicated (Led Zeppelin Led Shmeppelin).
- Shm-reduplication is generally avoided or altered with words that already begin with shm-; for instance, schmuck does not yield the expected *schmuck schmuck, but rather total avoidance or mutation of the shm- (giving forms like schmuck shluck, schmuck fluck, and so on).
- Many speakers use sm- instead of shm- with words that contain a sh (Ashmont Smashmont, not *shmashmont).
Further phonological details revealed by Bert Vaux and Andrew Nevins' online survey of shm-reduplication can be found here 
Origins and sociolinguistic distribution
The construction appears to have originated in Yiddish and was subsequently transferred to English, especially urban northeastern American English, by Yiddish speaking Jews. It is now known and used by many non-Jewish English speakers. The construction also transferred into Modern Hebrew usage, as a productive derogatory prefix resulting in an echoic expressive, as in David Ben-Gurion's famous dismissal of the United Nations (UN), oom shmoom (UN Shm-UN) during a March 29, 1955 government meeting. "When an Israeli speaker would like to express his impatience with or disdain for philosophy, s/he can say filosófya-shmilosófya". In German-Yiddish the same construction is possible, too, for example: Visum-Schmisum (i.e.: visa permits which have been somehow obtained, possibly below the level of legality.)
Zuckermann (2009) mentions in this context the Turkic initial m-segment conveying a sense of "and so on" as in the Turkish sentence dergi mergi okumuyor, literally "magazine 'shmagazine' read:NEGATIVE:PRESENT:3rd person singular", i.e. "(He) doesn’t read magazines, journals or anything like that".
A similar phenomenon is present in most of the languages of the Balkan sprachbund, especially in colloquial Bulgarian where not only 'sh(m)-' and 'm-' but also other consonants and consonant clusters are used in this way, and its usage has its particularities that differ from what the English 'shm' indicates.
As a counterexample in linguistics
Shm-reduplication has been advanced as an example of a natural language phenomenon that cannot be captured by a context-free grammar. The essential argument was that the reduplication can be repeated indefinitely, producing a sequence of phrases of geometrically increasing length, which cannot occur in a context-free language.
- Holly Raybin (December 1, 1986). "The Baby". Jews for Jesus. Retrieved December 12, 2011.
- Christina Rexrode and Sarah Skidmore (December 7, 2011). "Shoppers say 'ho-hum' not 'ho-ho-ho' to sales". The Boston Globe. AP. Retrieved January 28, 2012.
- Penn Jillette and Teller (1992). Penn & Teller's how to play with your food. Villard Books. p. 35. ISBN 0-679-74311-1.
- Zuckermann, Ghil'ad (2009), Hybridity versus Revivability: Multiple Causation, Forms and Patterns. In Journal of Language Contact, Varia 2: 40–67, p. 49, where he also refers to Haig (2001) and Lewis (1967).
- P. Asenova. Main problems of the Balkan sprachbund. Veliko Tarnovo, Bulgaria. 2002. (Bulgarian: Асенова, П., Балканско езикознание. Основни проблеми на балканския езиков съюз. Велико Търново. 2002 г.)
- Manaster-Ramer, Alexis (1983). "The soft formal underbelly of theoretical syntax". Proceedings of the Chicago Linguistics Society 19: 256–262.
- Feinsilver, Lillian Mermin. "On Yiddish Shm-". American Speech 36 (1961): 302–3.
- Nevins, Andrew and Bert Vaux. "Metalinguistic, Shmetalinguistic: The phonology of shm-reduplication". Proceedings of the Chicago Linguistics Society annual meeting, April 2003.
- Southern, Mark. Contagious Couplings: Transmission of Expressives in Yiddish Echo Phrases. Westport: Greenwood, 2005.
- Spitzer, Leo. "Confusion Shmooshun". Journal of English and Germanic Philology 51 (1952): 226–33.