Okay, I had to look up shibboleth. Atomica says it's ultimately from a Hebrew word meaning torrent of water, and was used to discern one tribe from another. Hmm...[mental gears ticking]...in an arid land, people would have made their homes around a source of water, if possible; so, perhaps this is comparable to a family today saying, "Hi, we're the Smiths from Bubbling Springs"? Does that sound reasonable?