late 15c., refusel, "act of refusing to do something, rejection of anything demanded," from refuse (v.) + -al (2). The sense of "choice of refusing or taking," as in right of first refusal, is by 1570s. The earlier noun was simply refuse (late 14c., from Old French refus), which was common through 16c.
"a repelling; a check, a defeat; peremptory denial or refusal," 1610s, from rebuff (v.), or from French rebuffe or Italian ribuffo.
1520s, "refusal to grant what is requested or desired;" see deny + -al (2). Replaced earlier denyance (late 15c.). Sense of "act of asserting to the contrary, contradicting" is from 1570s; that of "refusal to accept or acknowledge" is from 1580s. In some 19c. uses, it really means "self-denial." Meaning "unconscious suppression of painful or embarrassing feelings" first attested 1914 in A.A. Brill's translation of Freud's "Psychopathology of Everyday Life"; hence the phrase in denial, popularized 1980s.