mysah

[A. Scott Chesnick-]

I think it is Yiddish
mysah (fabrication)

In use...at
http://www.innernet.org.il/archives/courage.htm
"However (what's a Purim play without a happy ending), the
 righteous man is aware of what is happening, and he appears to the knight (a dream?
mental telepathy?) and says, "Schlemiel!
Jews don't believe in dragons; they don't exist!
If all the King Arthur stories are one big bobbeh
mysah (fabrication), then even a complete incompetent like
you can win!" and he does, and he returns to the House of
Study, makes a big Kiddush (celebration) and lives happily ever after."