I remember when I went on my mission, I got a list of items they suggested I pack.
Said list included "thongs".
I had no idea what that meant, since for me, "thong" was a piece of leather, and I had no idea what I would need one of those for.
So I tried to ask around (this was in pre-Web days for me, I think) and gathered that a thong could also be a particularly skimpy piece of underwear. That didn't make much more sense, either, so I ignored the "thongs" entirely.
Only a couple of years later did I learn that "thongs" could *also* refer to flip-flips: so called, presumably, because of the thong that goes between your big toe and your second toe to stop your foot from slipping off the front. Which made more sense as an item to pack.
But seriously. That word might be common in Utah, but I had no idea what to make of it. Call them "flip-flops" or "shower shoes" or "bathing sandals" or something, or at least add a synonym or two.
(Or am I being provincial and "thongs" is indeed widely understood in Anglophonia as meaning the footwear?)