While we largely think of the word ruminating as the art of thinking deeply about something, it has it’s origins in the act of digestion. Specifically in ruminant animals like the cow.
From Wikipedia:

A ruminant is a mammal that digests plant-based food by initially softening it within the animal’s first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called “ruminating”.

Therefore, it should be no surprise that another common phrase used for thinking deeply about something is “chewing the cud”.
So, to recap, ruminating is the processing of nutrition that has already been processed once and needs to be further processed to be fully digested.
Now that we know the origin, and the process, of the meaning as it relates to food digestion, I’d like to take this opportunity to suggest we better apply this action to the digestion of information.
The thing is, that we are bombarded by so much new information that we simply “swallow” it and move on. Perhaps we think about it in the moment and think we have absorbed something of value. But, like a ruminant beast, such processing can not have the same deep nutritional value as ruminating on those same things. In other words, learning something, letting it settle in, then spending further time processing it again at a much deeper level.
So, instead of exposing yourself to the constant stream of new information and knowledge this age affords us, consider spending some time “chewing the cud” of knowledge you already have. Spend some time ruminating on it — breaking it down — and by doing so make it more digestible and, therefore, nutritional.
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