1580s, with a capital -c-, "resembling Cynic philosophers," from cynic + -al (1). By 1660s (with a lower-case -c-) the meaning had shaded into the general one of "disposed to disbelieve or doubt the sincerity or value of social usages or personal character or motives and to express it by sarcasm and sneers, disparaging of the motives of others, captious, peevish." Related: Cynically.
Cynical expresses a perverse disposition to put an unfavorable interpretation upon conduct, or to exercise austerity under profession of a belief in the worthlessness of any offered form of enjoyment. Misanthropic expresses a hatred of mankind as a race. Pessimistic is primarily and generally a philosophical epithet, applying to those who hold that the tendency of things is only or on the whole toward evil. [Century Dictionary]