True, there is nothing about the devil in the derivation. The name Desdemone comes from δυσδαίμων that is δυσ (bad) +δαίμων (also had the meaning of "luck" in ancient greek, NOW it means "demon") meaning "ill-fated".
This does not mean "of the devil" in Greek. του διαβόλου would be "of the devil," transliterated: tou diabolou. "Of the demon" would be tou daimona (του δαίμονα). Damon is closer. However, I am not entirely certain of the standard meaning of the name, either. In koine Greek, ill-fated would be "kakotuchos" (κακότυχος). In Latin, it would be "calamitosa."
It is unlikely that it is Greek for "of the devil" as Greek theology has no devil - it has a lord of the underworld which, unlike the Christian connection to hell or a place for evildoers after death, the underworld is the place where all souls go after death, good and bad. Therefore the Greeks are unlikely to have a word in connection a Christian spiritual figure.