The headword is an Homeric adjective (Iliad 1.248, and Homeric Hymn to Apollo 4); also in Hesiod and Pindar. (The scholia to the Iliad passage gloss it differently: ὁ ἡδύς ἐν τῳ̂ λέγειν ).
Probably taken from the Synagogè (Lexica Segueriana 242.12), the source of which could be Herodian, Partitiones 45.12 or an interpolated gloss -– at least according to K.Latte -- of Hesychius, Lexicon eta137.