Treyf (sometimes spelled treif or treyfe) is a Yiddish word used for something that’s not kosher. The word treyf is derived from the Hebrew word treifah, which appears several times in the Bible and means “flesh torn by beasts.” The Torah prohibits eating flesh torn by beasts, and so the word treifah came to stand in for all forbidden foods. A ham and cheese sandwich? Very treyf.
Pronounced: TRAYF, Origin: Yiddish, not kosher