Green’s Dictionary of Slang

(US) one who enjoys indulging in sexual fondling and caresses.

1928		V. Hurst Big Game 22: A girl can’t afford to let herself get the reputation of being a petter.
1951		S. Lewis World So Wide 111: So naive in believing that every woman ought to be a college-campus petter!
1952		Lait & Mortimer USA Confidential 19: Raids on penny-ante poker games, park-petters and ginmills.