The Neighs Have It
“Champing at the bit,” often mispronounced as “chomping” (champing means to grind or chew) refers to a racehorse impatiently chewing the metal bit in his mouth as he eagerly waits to start his race.
A trained eye can gauge the age of a horse by its teeth, so the saying “Don’t look a gift horse in the mouth” reminds those who receive gifts not to over-scrutinize them and seem ungrateful.
In politics and other fields, a “dark horse” candidate is comparatively unknown and obscure. The term began in 17th century horse racing and applied to little-known and hard-to-put-odds-on horses which were entered into races.