Riding a hobby horse
The phrase "hobby horse," meaning someone's pet idea, derives from the wooden ponies children ride and ride and ride without getting anywhere. "Everyone has his hobby horse!" said Methodism's founder, John Wesley. He was referring to one's dwelling to excess on a pet theory. The first part of the name for this stick horse originally signified a small Irish horse, called a hobyn or dobbin. Children's devotion to this toy inspired the extension of its meaning to any favorite pastime or trivial pursuit. The toy originally came from a festival held in England in mid-May. The Morris Dance featured an imitation horse's head carried on a stick by a rider. Children caught on.
To curry favor
Today, this expression includes the word to groom or "curry," but not the horse's name. Originally, the horse in this phrase was Fauvel (for fallow-colored or chestnut), from a 14th-century French satire. He was a symbol of cunning and deceit and, therefore, to groom him was to bring out those qualities in oneself. Over the years, however, English speakers changed the French name to a more common and suggestive English noun. But the expression still means to brush or flatter someone in a way to gain an end or favor.