Likewise or similarly in other lexica; see the references at Photius kappa633 Theodoridis (and kappa 1436).
This particular genitive plural (already under alpha 425) is first attested in Synesius (Hymns 1.624) and Origen (Selecta in Psalmos PG 12.1509). However it seems to have been a variant of keuqmw=n in Homer, Iliad 13.29: a)/talle de\ kh/te' u(p' au)tou= / pa/ntoqen e)k keuqmw=n "and sea creatures came gamboling to him [Poseidon] out of their lairs, from every quarter". Apollonius in his Homeric Lexicon s.v. keuqmw=nes accounts for keuqmw=n in the passage as a syncope of keuqmw/nwn, and the D scholia ad loc. have the reading pa/ntoqen e)k keuqmw/nwn.
It is instead assumed that this passage uses a distinct noun keuqmo/s, a hapax in Homer, with the same meaning. The dispute is noted in the scholia vetera: "some consider it a syncope, while others posit keuqmo/s, like te[u]qmo/s, in the Ionic dialect, [keuqmo/s:keuqmw/n] like baqu/leimos:baqulei/mwn." Aristonicus (1 BC-1 CE), De signis Iliadis ad loc. posits the keuqmo/s reading as a reason why the passage was marked by editors of the Iliad with a diple; and keuqmo/s was used unambiguously by Callimachus (Hymn to Zeus 34: keuqmo/n) and Lycophron (Alexandra 317: keuqmw=|). Of course this only proves that Hellenistic scholarship had decided keuqmo/s existed as a separate noun.