So, I read that French même, Spanish mismo, and Italian medesimo, all meaning “same”, all derive from Latin metipsimum < metipsissimum < -met + ipse + -issimus.
Now, I hadn’t heard of -met, but Wiktionary has an article on it, saying:
At roughly that point I recognised it from Temet nosce, the phrase used in The Matrix to translate “know thyself” (rather than the usual translation of the original Greek Γνώθι σαυτόν, Nosce te ipsum).
It stands to reason that Romansh medem/madem also comes from the same source, so I thought I might derive the Engadinese word for “same” similarly. (That’s only western and central Romansh, though; Ladin has listess, presumably from the same route as Italian stesso, i.e. st + ipsu < istum ipsum.)
So I thought, what would be the equivalent of -met ipsissimum?
I don’t know of a clitic for “self”, but ipse is presumably εμαυτόν σ(ε)αυτόν etc., or perhaps αυτός; and -issimus would be -(ό/-ώ)τατος (with the vowel belonging to the stem of the adjective).
So ipsissimum would be something like αυτότατον—though I’m not certain of the stress. For “Greek stressed like Latin”, I’d have to know the quality of the alpha in the ending, which I can’t find out right now, so I’ll assume it’s short, in which case the stress would go on the antepenult.
So perhaps the word for “same” could end up something like τόδατ todat? Not sure, but it’s an idea.
(While doing research for the vowel, I came across -γε as in έγωγε έμοιγε, but that clitic seems to be restricted to only three or four forms. Still, it might give -γε αυτότατος > γαυτόδατ gautodat?)