Green’s Dictionary of Slang

1. the head, esp. in the context of eating.

1842		Whip & Satirist of NY & Brooklyn (NY)1 Oct. n.p.: [R]eplete with all the delicacies the season can afford for our ‘peckers’ .
1851		R.S. Surtees Young Tom Hall (1926) 59: [of a horse] He’d be constantly having his pecker in the manger, and peckers in mangers cost money.
1852		Bell’s Life in Sydney 4 Sept. 3/1: The said bonnet being perched over her pecker.
1853		R.S. Surtees Mr Sponge’s Sporting Tour 166: When I saw the critter’s great pecker steadily down in his plate, I thought I would try and steal a march upon him.
1904		Sydney Sportsman (Surry Hills, NSW) 4 may 1/3: [A] Mandarin of the umteenth rank, branded on the pecker with a pretty prismatic pimple.

2. an eater.

1861		C.C. Robinson Dial. Leeds n.p.: He’s a rare pecker [EDD].
1873		Sl. Dict. 249: Peck, A hearty eater is generally called ‘a rare pecker’.
1881		Leeds Times 19 Nov. 7/6: He’s known to be a rare pecker at summat to heyt.
1890–1904		Farmer & Henley Sl. and Its Analogues.

3. the appetite [B&L suggest -er sfx² ].

1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.