In Hebrew the word (שִׁׁבֹּלֶת) means “ear (of corn)”.
In the book of Judges the word “Shibboleth” is used to distinguish the Ephramites from the Gileadites. The former’s dialect lacked the sh-phoneme. We read in chapter 12:6 about a test:
וַיִּלְכֹּד גִּלְעָד אֶת-מַעְבְּרוֹת הַיַּרְדֵּן, לְאֶפְרָיִם; וְהָיָה כִּי יֹאמְרוּ פְּלִיטֵי אֶפְרַיִם, אֶעֱבֹרָה, וַיֹּאמְרוּ לוֹ אַנְשֵׁי-גִלְעָד הַאֶפְרָתִי אַתָּה, וַיֹּאמֶר לֹא.
5 And the Gileadites took the fords of the Jordan against the Ephraimites; and it was so, that when any of the fugitives of Ephraim said: ‘Let me go over,’ the men of Gilead said unto him: ‘Art thou an Ephraimite?’ If he said: ‘Nay’;
וַיֹּאמְרוּ לוֹ אֱמָר-נָא שִׁבֹּלֶת וַיֹּאמֶר סִבֹּלֶת, וְלֹא יָכִין לְדַבֵּר כֵּן, וַיֹּאחֲזוּ אוֹתוֹ, וַיִּשְׁחָטוּהוּ אֶל-מַעְבְּרוֹת הַיַּרְדֵּן; וַיִּפֹּל בָּעֵת הַהִיא, מֵאֶפְרַיִם, אַרְבָּעִים וּשְׁנַיִם, אָלֶף.
6 then said they unto him: ‘Say now Shibboleth‘; and he said ‘Sibboleth‘; for he could not frame to pronounce it right; then they laid hold on him, and slew him at the fords of the Jordan; and there fell at that time of Ephraim forty and two thousand.
After the inhabitants of Gilead inflicted a military defeat upon the tribe of Ephraim (around 1370–1070 BC), the surviving Ephraimites tried to cross the Jordan River back into their home territory and the Gileadites secured the river’s fords to stop them. In order to identify and kill these refugees, the Gileadites put each refugee to the above described test.