Green’s Dictionary of Slang

(UK Und.) one who lures a victim into a crooked game of cards or dice.

1592		Greene Blacke Bookes Messenger 3: A Table of the words of Art lately deuised by Ned Browne and his associates, to Crosbite the old Phrases used in the manner of Conny-catching. He that drawes the fish to the bait, the Beater.
1608		Dekker Belman of London F2: Sometimes likewise this Card-cheating [...] is called Batt fowling, and then the Setter is the Beater, the foole that is caught in the net, the bird.