cf. Synagoge pi748, and Photius, Lexicon pi1443, both of which offer only the first of the two glosses on this masculine nominative singular. See also already Hesychius pi4133, who gives that same glossing phrase in the masculine nominative plural to the plural prwqh=bai (quoted from Homer, Odyssey 8.263; cf. the D scholia there).
The headword literally means first-youthed, a concept difficult to convey with a single English word. Literary attestations of this form of the word prior to the Suda are infrequent, but include Apollonius Rhodius, Argonautica 1.132, and Lucian, Dialogues of the Dead 15.2.
For a different form of the same word see pi 2942.