Green’s Dictionary of Slang

robin hog n.

[ety. unknown; ? simply derog. since pig n. (2a) is not coined until early 19C]

a constable.

[UK]E. Hickeringill Priest-Craft I 48: Calling upon the Jaylors, the Sumners, the Rascals, the Robin Hogs, and Bumbailiffs, to help you to smother a Book, and stop it in the Press.