The headword, a Doric and Aeolic form, is the nominative (and vocative) singular of the feminine Attic substantive sa/lh; see generally LSJ s.v. Photius s.v. (see next note) adds 'thus Aeschylus'. This dialect form of the noun is nowhere extant in Aeschylus, but in his fr. 319 Nauck the gloss sa/lh ga\r h( fronti/s attaches to the phrase a)salh\s mani/a ("thoughtless madness"). According to Chantraine, the noun sa/lh was formed by "inverse derivation" from a)salh\s.
[1] The gloss is a feminine noun in the nominative singular; see generally LSJ s.v. and cf. phi 733. Same glossing in Hesychius, Photius' Lexicon (sigma43 Theodoridis), and s.v. sa/los in the Synagoge. See also sigma 59 (end).