Mid 16th century. From post-classical Latin accismus from Hellenistic Greek ἀκκισμός coyness, affectation from ancient Greek ἀκκίζεσθαι to affect indifference, to affect ignorance, dissemble, to affect to be shocked, to be coy (from Hellenistic Greek ἀκκώ bogey, that nurses frighten children with (from the same Indo-European base as classical Latin Acca, name of the shepherd's wife who brought up Romulus and Remus) + -ίζεσθαι) + -μός, suffix forming nouns.