Judges 12:6 - Matthew Poole's English Annotations on the Holy Bible

Shibboleth signifies a stream or river, which they desired to pass over; so it was a word proper for the occasion, and gave them no cause to suspect the design, because they were required only to express their desire to go over the Shibboleth or river. He said Sibboleth. It is well known, that not only divers nations, but divers provinces, or parts of thee same nation, who use the same language, differ in their dialect and manner of pronunciation. He could not frame to pronounce it right, or rather, he did not frame or direct himself to speak so, or to speak right, i.e. so as he was required to do it. The Hebrew text doth not say that he could not do it, but that that he did it not, because he, suspecting not the design of it, uttered it speedily according to his manner of expression. At that time; not in that place, at the passages of Jordan, but in that expedition, being slain either in the battle, or in the pursuit, or at Jordan.