Here's the breakdown:
* Ruminants have a four-chambered stomach. They first swallow their food, then regurgitate it back up into their mouth to be chewed again. This process is called rumination.
* Chewing the cud refers to the act of ruminating, where the animal chews their partially digested food to break it down further.
The idiom's meaning:
The idiom "chew your cud" is used to describe someone who is thinking deeply or pondering something, often in a slow and contemplative manner. The image of a ruminant animal chewing its cud evokes the idea of careful, thorough consideration.
Origin:
The idiom has been used in English since at least the 16th century. Its use likely stemmed from the observation of ruminant animals and the association of their chewing process with deep thought.
Example:
"I'm going to go home and chew on this problem for a while before I make a decision."