late 14c., "action of turning aside from truth, corruption, distortion" (originally of religious beliefs), from Latin perversionem (nominative perversio) "a turning about," noun of action from past participle stem of pervertere (see pervert (v.)). Psychological sense of "disorder of sexual behavior in which satisfaction is sought through channels other than those of normal heterosexual intercourse" is from 1892, originally including homosexuality.
Perversions are defined as unnatural acts, acts contrary to nature, bestial, abominable, and detestable. Such laws are interpretable only in accordance with the ancient tradition of the English common law which ... is committed to the doctrine that no sexual activity is justifiable unless its objective is procreation. [A.C. Kinsey, et.al., "Sexual Behavior in the Human Male," 1948]