SHIBBOLETH
“spike”; or “river”, “watercourse”.
In the local Ephrainite dialect, the lingual sibilant phoneme “s” took the place of the palatal sibilant phoneme “sh” at the beginning of words.
When Jephthah, leader of the Gileadites, defeated the Ephraimites and took the fords of the Jordan, many fugitives wanted to cross the river. The term “shibolet” that the victors made the fugitives utter became “sibolet” in the mouths of the Ephraimites, betraying them.
Thus discovered, they were executed on the spot (Judg. 12:5, 6). It is also possible that the Gileadites retained an archaic pronunciation of the phoneme “sh” similar to that of a soft z, and that the Ephraimites could not imitate it correctly.