"Meh" might come from the Yiddish, via the Simpsons. From the Oxford English Dictionary:
Etymology: Probably < Yiddish me be it as it may, so-so (1928 or earlier), probably imitative.
Probably popularized by the U.S. cartoon series The Simpsons , in which its earliest use was in the episode Sideshow Bob Roberts , first broadcast on 9 Oct. 1994.
