Green’s Dictionary of Slang

coll n.

[cull n.1 (2)]

1. a dupe, a silly fellow.

[UK]T. Jordan Walks of Islington and Hogsdon II ii: We are no colls you know, you must not flam us.
[UK]C. Cotton Compleat Gamester 7: They can discover some unexperienc’d young gentleman [...] that is come to this School of Virtue, being unskill’d in the quibbles and devices there being practised; these they call Lambs, or Colls.

2. a man, a fellow, a chap; thus rum coll, the king.

[UK]Canting Academy, or the Pedlar’s-French Dict. 113: The King The rum Coll. [Ibid.] 114: Drunkard A Buesing Coll.