The headword is a feminine noun in the nominative singular; it may be drawn from a literary source (of which there are several options) or it may be a generic lexical reference. Among the most similar glosses are scholia to the works of Gregory of Nazianzus, who uses the headword three times in this form (PG 35.1140.6, 36.460.13, 16). See also Etymologicum Gudianum 504.48, 54. Adler also cites Lexicon Ambrosianum 504.
The headword is generally taken as an alternative form of the more common skotomh/nh, sigma 679 (so e.g. LSJ s.v., and compare Et.Gud. with Hesychius sigma1130), but some ancient sources connected the second element -maina to the verb mai/nomai ('be insane'); e.g. Etymologicum Magnum 719.34-5.