1911 Encyclopædia Britannica/Shibboleth
SHIBBOLETH, a Hebrew word, meaning an ear of corn or a stream or river, from shābal, to grow, increase, flow, used by Jephthah, probably in the second sense with reference to the river Jordan, as a test-word to distinguish the Ephraimites, who were unable to pronounce the sh, from the men of Gilead (see Judges xii. 6) at the passage of the Jordan. The word ciceri was similarly used at the time of the massacre of the French known as the Sicilian Vespers, for they betrayed their nationality by their inability to pronounce it. The term has also come generally to mean a watchword, catch-phrase or cry, to which the members of a party adhere after any significance or meaning which it may have imported has disappeared.
See Alphabet, i. 725, for a discussion of the sibilant difficulty involved in the test of Judges xii. 6.