The headword is apparently an alternative form of the pluperfect indicative middle/passive, third person singular, of paiwni/zw ('sing Paeans for', 'hymn', 'celebrate'; pi 884). Canonically the form should be e)pepaiw/nisto (cf. epsilon 2062). The form given here is attested only once elsewhere (apart from the derivative entry in ps.-Zonaras): Gregorius Pardus, Commentarium in Hermogenis librum Peri methodou deinotetos 7.1.1246.8.
The original form of this entry may well be preserved in Hesychius epsilon4420: e)pepaiw/nisto: e)pefh/misto. There the headword is in the expected form, though the gloss is somewhat troubling: e)pefh/misto, from fhmi/zw should mean 'had been uttered' without any celebratory connotation. On the other hand, the Suda's eu)fh/misto would normally mean 'had been kept in ritual silence.'