The words idiom and idiot differ only in the final letters: t and m. So I was wondering - do these words have a common root? If so, how have the t and m changed this root?
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I suspect this may be general reference, but from the OED:
Etymology of idiot:
Etymology of idiom:
So it appears that they share a very distant root (idio-) but their meanings would have been distinct even in ancient Greece by virtue of the endings.