"refuse to avow; disclaim knowledge of, responsibility for, or connection with," late 14c., from Old French desavouer (13c.), from des- "opposite of" (see dis-) + avouer "acknowledge, accept, recognize" (see avow). Related: Disavowed; disavowing.
suffix forming nouns of action from verbs, mostly from Latin and French, meaning "act of ______ing" (such as survival, referral), Middle English -aille, from French feminine singular -aille, from Latin -alia, neuter plural of adjective suffix -alis, also used in English as a noun suffix. Nativized in English and used with Germanic verbs (as in bestowal, betrothal).
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Harper, D. (n.d.). Etymology of disavowal. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/disavowal