Ah, so Perseus is the culprit here. Callimachus, fragment 103 (= Plutarch, Quest. Conv. 677b1ff.), reads as follows:
καί μιν Ἀλητιάδαι, πουλὺ γεγειότερον
τοῦδε παρ' Αἰγαίωνι θεῷ τελέοντες ἀγῶνα,
θήσουσιν νίκης σύμβολον Ἰσθμιάδος,
ζήλῳ τῶν Νεμέηθε· πίτυν δ' ἀποτιμήσουσιν,
ἣ πρὶν ἀγωνιστὰς ἔστεφε τοὺς Ἐφύρῃ.
No one, as far as I know, suggests a variant reading for Νεμέηθε. The word νεκυό-ηθε, besides making no sense, won't fit metrically. Here is the original 1940 LSJ print version:
Adv. Νεμέαθεν, poet. —ηθε, from Nemea, Call. Fr. 103.. Same in Diogenes' online version.
Even Homer nods, now and then. So does Perseus.