A custom, phrase, or practice that distinguishes one group from another — particularly one used to identify outsiders who cannot correctly reproduce it.

From the Hebrew word meaning an ear of grain or a flowing stream, used in the Book of Judges as a password by the Gileadites to identify Ephraimites who could not pronounce the 'sh' sound.

Has come to refer more broadly to any long-held belief or practice that is seen as outmoded or no longer relevant to a particular group.

The original biblical episode is considered one of the earliest recorded examples of using phonological differences to identify enemy combatants.

During the Second World War, Allied forces used the word lollapalooza as a shibboleth, as Japanese speakers struggled to pronounce the initial 'l' sounds.