Shank’s pony
Shank’s pony is a jocular expression that means on foot, and dates in various forms, ‘shank’s nag’, ‘shank’s mare’ as well as ‘shank’s pony’ from the early 18th century. The shank is the lower part of the leg between the ankle and the knee, now generally reserved for animals like, horses, sheep etc but, during earlier centuries, it was also part of the human leg. Attempts to theorise that Shank was a real person are all spurious.