The headword is a feminine noun in the accusative singular; see LSJ s.v. mo/rfwsis. The probable source, as is routinely observed, is the New Testament: Romans 2:20. (See also 2 Timothy 3:5.) Note, nevertheless, that the nominative singular forms of both the headword itself and the first gloss appear at Theophrastus, On the Causes of Plants 3.7.4.
[1] The first gloss is a masculine noun in the accusative singular; see LSJ s.v. sxhmatismo/s. The second gloss is the same form as the lemma, from the substantive ei)kw/n; see LSJ s.v. The headword is identically glossed in Photius' Lexicon (mu543 Theodoridis), Hesychius mu1698, and the Synagoge; cf. Lexica Segueriana 303.23 and ps.-Zonaras 1370.23. Adler also cites Boysen's Lexicon Seguerianum.