Κηκάς is used in Callimachus fr.656 κηκάδι σὺν γλώσσῃ "with an abusive tongue", and Nicander, Alexipharmaca 185 πιοτέρην ὅτε βότρυν ἐσίνατο κηκὰς ἀλώπηξ "when the mischievous fox plundered the fat grapes". κηκασμός is in Lycophron Alexandra 545, 692.
Otherwise, the words only occur in lexica, κηκάς from Hesychius on and κηκασμός next attested in the scholia to Lycophron, Pseudo-Zonaras and the Suda. The Etymologicum Parvum and Etymologicum Magnum derive κηκάς from κακός , a derivation the LSJ repeats with reservations. The Etymologicum Parvum is the first lexicon to gloss κηκάς as λοιδορία ; the word is absent from Photius.