The edge of something is the קָצֶה (kah-TSEH); someone “on the edge” or extreme is קִיצוֹנִי (kee-tsoh-NEE).
But someone moderate or level-headed – in ideology or in relationships – is מָתוּן. My 2am not-delving-into-it theory is that the word is related to מָתְנַיִם – hips (moht-NAH-yeem), since the hips comprise approximately the midsection of the body.
The first מִשְׁנָה – Mishnah – of the Ethics of the Fathers – פִּרְקֵי אָבוֹת (peer-KEH-ee ah-VOHT) calls upon the leaders of the Jewish people to be מְתוּנִים בַּדִּין (meh-too-NEEM bah-DEEN) – they should be moderate in judgment. But whether the משנה actually means the word מתונים as moderate or something else is up for debate among the commentators.
Another example: I just watched The Godfather. Whether Al Pacino’s character, Michael is קיצוני or מתון is also up for debate.
What do you think?