denial (n.)

early 14c., "declare to be untrue or untenable," from Old French denoiir "deny, repudiate, withhold," from Latin denegare "to deny, reject, refuse" (source of Italian dinegarre, Spanish denegar), from de "away" (see de-) + negare "refuse, say 'no,' " from Old Latin nec "not," from Italic base *nek- "not," from PIE root *ne- "not."

From late 14c. as "refuse, refuse to grant or give," also "refuse to acknowledge, disavow, disown." Sense of "refuse access to" is from 1660s. Related: Denied; denying.

I may not understand what you say, but I'll defend to your death my right to deny it. [Albert Alligator, "Pogo," Sept. 26, 1951] 

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).

"act of denying one's own wishes; refusal to satisfy one's own desires," 1640s, from self- + denial.

Self-denial is to be presumed wise, necessary, or benevolent, unless indication is given to the contrary ; it may be the denial of selfishness; it may be not only the refusal to take what one might have, but the voluntary surrender of what one has ; it may be an act, a habit, or a principle. [Century Dictionary]

Related: Self-denier; self-denying (adj.) is by 1630s as "involving self-denial," also "characterized by or involving denial of one's self."