Adler cites as a source two entries (597, 673) in the unedited Ambrosian Lexicon. The aim would seem to be to illustrate an alternative way of saying "Greek" (as opposed to the common *(Ellhniko/s; cf. epsilon 838).
The phrase in the supplementary lemma appends the same form of the adjective to a feminine noun, which would obviously suggest that the adjective is of the two-termination variety. However, if that was true by the time of these lexica, it was not so earlier: see LSJ s.v., citing e.g. Athena Hellania in Euripides, Hippolytus 1121.