Feyokien wrote:
Beating a dead horse
The most common animal in English idioms is horses.
Some are obvious: Beating a dead horse, neck and neck,ahead by a nose, horse of a different color, riding roughshod, never look a gift horse in the mouth, a real work horse, horsing around, horseplay.
Others are more obscure,but are also connected to horses.
The phrase "that really gets my goat" comes from the practice of providing a thoroughbred race horse with a goat as a companion while the horse is being shipped around to the race tracks around the country. If a rival wanted to sabotage your horses performance he might steal your horse's goat friend to mess up the horse's psychological fitness.
The phrase "Hobson's choice", meaning "the choice between what is offered, or nothing at all" comes from Mr. Hobson, a guy who rented horses in London in the 18th Century (kind of the Hertz of his day).