hobbyhorse

The hobbyhorse is a toy of yesteryear, dating back to a homespun era predating automobiles. In the 1400s, the word hobby could refer to a real-life horse of small or average size. It soon came to refer to the horse costume worn by one participating in a morris dance or burlesque performance, and then, later, to the child's toy. Another meaning of hobbyhorse was "a favorite pursuit or pastime"; our modern noun hobby ("an activity that one does for pleasure when not working") was formed by shortening this word. From "pastime," the meaning of hobbyhorse was extended to "a subject to which one repeatedly returns." The sense is typically encountered as part of such metaphorical phrases as "get on one's hobbyhorse" or "ride one's hobbyhorse."