“Chew the cud” means to think something over carefully. The phrase comes from how cows bring food back up and chew it again.

“A dark horse” started in horse racing for an unknown but promising horse, then spread to politics and everyday English.

This idiom began in real seafaring life, then shifted into everyday English for feeling confused, uncertain, or out of place.

Ambiguous means unclear or open to more than one meaning. Ambivalent means having mixed feelings about something.

“Ride roughshod over someone” once referred to actual trampling by a horse. Now it means treating people harshly or ignoring their rights.