Английский Этимологический словарь - pet (1)

- "animal," 1508, originally Scot. and northern England dial.; sense of "indulged child" is recorded slightly earlier than that of "animal kept as a favorite." Of unknown origin, but probably associated with or influenced by petty. The verb is 1629 meaning "treat as a pet;" the sense of "stroke" is first found 1818. Slang sense of "kiss and caress" is from 1924.