The headword -- closer to the glossing word in Greek than it sounds in translation -- is a poetic noun, used by Lycophron at Alexandra 1134; otherwise attested only in lexicography and grammars. Hesychius mu2047 glosses it as me/myis, o)/neidos, ai)=sxos. See also mu 1331.
Chantraine (s.v. mw=mos) suggests that mw=mar may be an archaic form or perhaps a false archaism, possibly influenced by mu=mar cited by Hesychius mu1867 (see alpha 1673). He says also that an etymological relationship has been proposed between mw=mar and mu=mar, assuming a rare alternation between ō and ū as in zwmo/s (zeta 136) and zu/mh (zeta 197).
[1] cf. ps.-Herodian 88 and (according to Adler) the Ambrosian Lexicon.
[2] cf. Festus: momar Siculi stultum appellant "Sicilians call a stupid man momar". See web address 1.
[3] This equivalence is unintelligible as it stands. (No textual corruption is indicated in Adler.)