Green’s Dictionary of Slang

a tooth.

1811		Lex. Balatronicum n.p.: Cog. A tooth. A queer cog; a rotten tooth. How the cull flashes his queer cogs; how the fool shews his rotten teeth.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
1859		Matsell Vocabulum.