Ben Zimmer provides some etymology:
The British poet W.H. Auden didn’t think much of the first lunar landing, and he wrote a poem about it.
Worth going to see? I can well believe it.
Worth seeing? Mneh! I once rode through a desert
and was not charmed: give me a watered
lively garden, remote from blatherersAuden’s mneh sounds like [humorist Leo] Rosten’s mnyeh, but Auden was no Rosten, to say the least. Still, since he was living in New York in 1969, we can imagine him hearing the Yiddish-style expression of apathy and finding it an appropriate vehicle for his lack of interest in the exploits of Armstrong and Aldrin. I found a 1973 collegiate poetry journal on Google Books, which had this to say: “Stanza six offers a new word to our word-hoard: the exclamatory Mneh! A pseudo-borrowing from Mad magazine?” Auden reading Mad in New York is an enticing image, of course. But I don’t think he picked up the expression that way, despite the fact that founding editor Harvey Kurtzman gave the magazine a Yiddish spin.