There is a curious construct in American English in which a word is stated and then repeated with the prefix "schm-" or "shm-" in order to indicate the speaker's dismissive attitude toward a concern that somebody else has. For example:
"Smokers have lower life expectancies? Correlation, schmorellation—I'm going outside for another cancer stick."
Is the commoner or more "correct" spelling "shm-" or "schm-"? Is this construction used outside the US? What is its origin?