In Yiddish’s arsenal of gently mocking dismissal, no single feature is quite as interesting as the “shm-” replacement. Linguistically, this is a relatively unusual operation whereby the initial consonant or cluster of consonants is replaced by the segment “shm-” to express one’s general disdain for the thing in question. The English phrase “fancy-shmancy,” for example, is a direct borrowing from the Yiddish. It indicates the speaker’s attitude of “la-di-da” to some perceived snobbery. English has a few more-or-less native phrases that capture the basic tenor of the technique, as in “airy-fairy” or “artsy-fartsy.” But in those cases, each of the words in the pair already exists in the language, and it is not a productive pattern; you can’t just make up new pairs. In Yiddish, by contrast, it is a very productive pattern and can be applied at will to almost any noun: “fidl—shmidl” (I’m not a fan of the violin); “hint—shmint” (dogs, meh); and so forth.
Historically, this feature has its roots in Middle High German. In that context, there were a number of options for satirical initial consonant substitutions. What is interesting is that these forms dropped out of German but were retained in one form or another in Yiddish dialects until the mid-nineteenth century, when “shm-” seems to have taken off and become the standard form. The few instances of it in modern German are reintroductions from Yiddish, which not only preserved the technique but also made it iconic.
Dr. Jordan Finkin, “What is Affective Disposition, and How Does Yiddish Excel at It?”, The American Israelite (19 August 2021), 6.