Definition of hobby horse

The term "hobby horse" originally referred to a toy horse made from materials such as wood or painted tin, usually ridden by a child for imaginative play. Its exact origin is unclear, but it's believed to have been commonly used by children in England during the 18th and 19th centuries. The word "hobby" originally meant a small horse ridden for leisurely purposes, such as hunting or dwarfed versions of a warhorse. The term "hobbyhorse" combined this meaning with the word "horse" to create a toy that could be ridden for entertainment, whether for children or adults. The use of "hobbyhorse" with its modern meaning — a person who has an obsessive interest in a recreational activity — may have arisen from the idea that someone with a hobby could be just as passionate and dedicated as a horse for a specific task. However, the precise origin of this metaphorical use is not widely documented.