Green’s Dictionary of Slang

ard n.

[? related to the Nordic ard, plough, a term used in archaeology to describe the style of plough in use during the Bronze Age; note Partridge rejects this use]

(UK Und.) the foot.

[UK]Farmer & Henley Sl. and Its Analogues.
[UK]Partridge DSUE (1984) 24/2: C.17–early 19.