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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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closed as general reference by Mitch, Kris, jwpat7, Mahnax, Hugo Apr 18 '12 at 7:25

This question is too basic; it can be definitively and permanently answered by a single link to a standard internet reference source designed specifically to find that type of information.If this question can be reworded to fit the rules in the help center, please edit the question.

NOAD traces both back to Gr idios 'own, private', but the difference seems to stem to Gr derivatives of this. – zpletan Apr 17 '12 at 21:19

I suspect this may be general reference, but from the OED:

Etymology of idiot:

ancient Greek ἰδιώτης private person, person without professional knowledge, layman, ignorant, ill-informed person, in Hellenistic Greek also common man, plebeian < ἴδιος private, own, peculiar (see idio- comb. form) + -ώτης -ote suffix

Etymology of idiom:

Hellenistic Greek ἰδίωμα peculiarity, property, peculiarity of style, form of language peculiar to a particular individual < ancient Greek ἰδιοῦσθαι to make one's own, to appropriate ( < ἴδιος own, private, peculiar: see idio- comb. form) + -μα (see -oma comb. form).

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.

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If you came up with that information by looking it up on-line, then, yes, it is general reference. – Mitch Apr 17 '12 at 21:51
@Mitch: the OED is only available (online) by subscription, so it's a bit harsh to call it general reference. – TimLymington Apr 17 '12 at 22:26
@Tim: The etymology is available for all here: etymonline.com/index.php?term=idiot&allowed_in_frame=0 – Hugo Apr 18 '12 at 7:28

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