shib·bo·leth 
(shĭbə-lĭth, -lĕth′)
(shĭbə-lĭth, -lĕth′)n.
1. A word or pronunciation that distinguishes people of one group or class from those of another.
2.
a. A word or phrase identified with a particular group or cause; a catchword.
b. A commonplace saying or idea.
3. A custom or practice that betrays one as an outsider.
[Ultimately from Hebrew šibbōlet, torrent of water, from the use of this word to distinguish one tribe from another that pronounced it sibbōlet (Judges 12:4-6).]