Shibboleth (IPA: /ˈʃɪbəlɛθ/[1] or IPA: /ˈʃɪbələθ/[2]) is any practice which is indicative of one's social or regional origin. However it usually refers to language usage. More specifically, it is any word whose pronunciation identifies its speaker as being a member or not a member of a particular group.
http://en.wikipedia.org/wiki/Shibboleth
