Green’s Dictionary of Slang

the highway.

1753		J. Poulter Discoveries (1774) 38: They dress out for a Gentleman, and get acquainted with the slaving Glokes of the Inns on the Panny; that is, the Ostlers on the Road.
1786		Whole Art of Thieving [as cit. 1753].
1799		‘Cant Lang. of Thieves’ Monthly Mag. 7 Jan. n.p.: Scamping on the Panny Going on the Highway to rob.