The headword phrase, deriving from a coinage by Aristophanes (see below) was proverbial: see Zenobius 5.65 and other paroemiographers.
The participle in the headword phrase is perfect middle/passive, masculine accusative singular, of the doubly compound verb parecaule/w. Hesychius glosses e)chulhme/non, and that singly compound version also appears in this passage. Both forms come ultimately from au)le/w, "I play the aulos" (alpha 4447).
[1] Aristophanes, Acharnians 681 (web address 1), with scholion; the aged chorus-members describe themselves thus.
[2] Homer, Iliad 11.390 (web address 2). The hero Diomedes [Author, Myth] (OCD(4) s.v.) is "dumb" of neither mind nor weapon; nor indeed is he dumb and without voice, as his boast in this passage testifies (Hainsworth pp. 268-9).