(plural shanks' mares)
- shanks' nag, shanks-nag, and variants (Scottish)
- shanks' pony and variants (UK, Australian)
The expression -- believed to be Scottish in origin -- derives from shanks' nag (shanks-naig 1774), referring to the use of shank to refer to the part of the human leg between the knee and ankle. One theory cites "shank's mare" derived from a horse-drawn lawn mower, manufactured by Shanks & Company Ltd. (founded 1853) which required that the human operator walk behind the device to guide the horse; however, references to the phrase in Scottish literature pre-date the existence of the Shanks lawn mower.