Joe Schmoe

Joe Shmoe (also spelled Joe Schmoe and Joe Schmo and "Yo Hschmo"), meaning 'Joe Anybody', or no one in particular, is one of the most commonly used fictional names in American English. Adding a "Shm" to the beginning of a word is meant to diminish, negate, or dismiss an argument (for instance, "Rain, shmain, we've got a game to play"). This process was adapted in English from the use of the "schm" prefix in Yiddish to dismiss something; as in, "Fancy, schmancy." While "schmo" ("schmoo," "schmoe") was thought by some linguists to be a clipping of Yiddish "schmuck", an etymology supported by the Oxford English Dictionary, that derivation is not universally accepted.

...
Wikipedia