mitis.

Of unclear origin, with multiple competing theories. The prevailing etymology connects Old Irish méth (“plump, fat”), Welsh mwyd (“act of soaking”), Welsh mwydion (“soft parts”) (from Proto-Celtic *meitos (“soft, plump”)); Old Irish mín (“soft; gentle, smooth; mild, tender, calm”) (Proto-Celtic *mīnis); and Old Irish moíth (“soft, tender”) (Proto-Celtic *moitos), together from Proto-Indo-European *meyh₁- (“mild, soft”). Other potential Indo-European cognates also point to a meaning like “pleasant”: Sanskrit मयस् (máyas, “pleasure, enjoyment, refreshment”), Avestan 𐬨𐬀𐬌𐬌𐬀𐬵 (maiiah, “pleasure”), Proto-Slavic *mìlъ (“soft, mild, gentle, agreeable, pleasant, sweet, dear”), Lithuanian mielas (“nice, sweet, cute”), Latvian mīls (“dear, cherished, beloved”), Old Prussian mijls (“dear”), Albanian mirë (“good, well”). De Vaan suggests that the root *meyh₁- is actually *meh₁i-, being originally an extension of *meh₁- (“to measure”). Alternatively, Oettinger compares Hittite 𒈠𒀀𒄿𒀭𒍣 (ma-a-i-an-zi, “to grow (up); to prosper”), reconstructing Proto-Indo-European *meyH- (“to ripen”); Kloekhorst rejects this on both semantic and formal grounds. Plötz suggests it to be a zero-grade extension of the prohibitive particle *meh₁i, specifically labeling it a derivative from *mh₁i-tis.