The headword is a neuter noun (related to the verb mhni/w: see mu 956, etc.) with three related meanings in LSJ: cause of wrath; (blood-)guilt; wrath. Its earliest occurrences -- in the first of these senses -- are in a phrase found twice in Homer (Iliad 22.358, Odyssey 11.73); mh/ toi/ ti qew=n mh/nima ge/nwmai. The scholia to neither of those passages use the present glossing term; see rather Hesychius s.v. (and Apollonius' Homeric Lexicon 112.24).
For the headword see also under delta 979.