shibboleth (n.) late 14c., the Hebrew word shibboleth, meaning "flood, stream," also "ear of corn;" in Judges xii.4-6.It was the password used by the Gileadites to distinguish their own men from fleeing Ephraimites, because Ephraimites could not pronounce the -sh-sound. Hence the figurative sense of "watchword" (first recorded 1630s), which evolved by 1862 to "outmoded slogan still adhered to."