shanks's pony

[felicityaw]

what is the dreivation?

[mykwyner]

To shank it means to walk, to use your legs (shank bones) for travelling. This developed into "shank's mare" which was sort of a joke about a poor man's horse (mare) being his own two legs (shanks). "Shank's pony" is some sort of play on that expression (maybe a short man walking).