sebboleth

Etymology
From, with reference to Judges 12:5-6: ‘Gilead then cut Ephraim off from the fords of the Jordan, and whenever Ephraimite fugitives said, “Let me cross,” the men of Gilead would ask, “Are you an Ephraimite?” If he said, “No,” they then said, “Very well, say Shibboleth.” If anyone said “Sibboleth”, but could not pronounce it, they would then seize him and kill him by the fords of the Jordan’ (New Jerusalem Bible).

Noun

 * 1) shibboleth