Same entry, according to Adler, in the Ambrosian Lexicon.
The headword is an adverbial form from the verb e)gkone/w, "I am quick/active" (web address 1); cf. epsilon 107, epsilon 108, epsilon 109. Noted also in several of the etymological lexica, it is very probably quoted here from Pindar, Nemean Odes 3.36 (web address 2), where it describes Peleus' capture of Thetis.