shibboleth
From Longman Dictionary of Contemporary Englishshibbolethshib‧bo‧leth /ˈʃɪbəleθ $ -ləθ/ noun [countable] formal PREJUDICEDan old idea, custom, or principle that you think is no longer important or suitable for modern timesOrigin shibboleth (1600-1700) Hebrew “stream”, used (according to the Bible) by the Gileadite people as a way of recognizing their enemies, who could not pronounce the sh properly