Yours, Etc.: Origins and Uses of 8 Sign-Offs
"mad, crazy, stupid," 1892, from Hebrew meshugga, part. of shagag "to go astray, wander." The adjective has forms meshugener, meshugenah before a noun.
(also meshigga or meshugah or meshiggah or mishugah or mishoogeh) Crazy; nutty: Mishoogeh or mishugah, spelled either way, means crazy
[1892+; fr Yiddish fr Hebrew; the variant pronunciations reflect major dialects of Yiddish]