The headword adjective occurs in Homer, Hesiod, and other early poets. (Later it is rare, generally referring to Homeric and Hesiodic passages; only Maximus Astrologus and Nonnus seem to use it in a original way.)
As to the glosses, in our opinion they have a double source:
A) The first, probably via Hesychius, is the scholia to Homer, Iliad 20.154, “Δυσηλεγέος: δεινοῦ, δυσκολοῦ, χαλεποῦ (scholia vetera and scholia recentiora) -- which explains χαλεπός here.
B) The second is from the scholia to Hesiod, Theogony 652: Δυσηλεγέος: δυσφροντίστου, δυσεκλύτου, κακοήχου (scholia vetera Di Gregorio), which explains κακόηχος .
[1] Meaning according to LSJ. The sense, in this context (in relation to the Hesiodic verse), is perhaps “bringing a sentiment of uneasiness, disquieting”.