Shibboleth

noun
1.
a peculiarity of pronunciation, behavior, mode of dress, etc., that distinguishes a particular class or set of persons.
2.
a slogan; catchword.
3.
a common saying or belief with little current meaning or truth.
noun
1.
a belief, principle, or practice which is commonly adhered to but which is thought by some people to be inappropriate or out of date
2.
a custom, phrase, or use of language that acts as a test of belonging to, or as a stumbling block to becoming a member of, a particular social class, profession, etc
shibboleth [(shib-uh-luhth, shib-uh-leth)]

In the Old Testament, shibboleth was a password used by the Israelites. It was chosen because their enemies could not pronounce it.

Note: By extension, a shibboleth is an often-repeated slogan. It also means an arbitrary test to prove membership in a group.

river, or an ear of corn. The tribes living on the east of Jordan, separated from their brethren on the west by the deep ravines and the rapid river, gradually came to adopt peculiar customs, and from mixing largely with the Moabites, Ishmaelites, and Ammonites to pronounce certain letters in such a manner as to distinguish them from the other tribes. Thus when the Ephraimites from the west invaded Gilead, and were defeated by the Gileadites under the leadership of Jephthah, and tried to escape by the “passages of the Jordan,” the Gileadites seized the fords and would allow none to pass who could not pronounce “shibboleth” with a strong aspirate. This the fugitives were unable to do. They said “sibboleth,” as the word was pronounced by the tribes on the west, and thus they were detected (Judg. 12:1-6). Forty-two thousand were thus detected, and “Without reprieve, adjudged to death, For want of well-pronouncing shibboleth.”