A recent bluffing-game word was merdivorous-dung-eating. When Kalleh mentioned it to me I thought of other eating-words that use the same -vorous suffix: carnivorous, herbiborous and omnivorous are all reasonably familiar.

But other like words, also meaning "_____-eating", instead use the suffix -phagous. They aren't common, but here is a list. Bacteria that eat oil (useful for dealing with an oil spill) are called _____phages -- I can't remember the prefix. Just last week "ophiophagous: Feeding on snakes" was bartleby.com's word of the day (which is the only reason I know of it). And there's even a -phagous word, coprophagous, that means exactly the same thing as our bluffing-game word merdivorous.

So query: why does English use a -vorous word in some cases and a -phagous word in others? Is there any pattern or historical reason?

And of course in medicine, there is the esophagus using the "phagous" root. Also, there is 'sarcophagus,' which has an interesting word history

BTW, I should have gotten "merdivorous" right. After I saw what others had chosen, I remembered the definition.

-vor- is Latin, -phag- is Greek. Ideally they should only be attached to their respective languages. There should also be quite a few doublets: carnivorous = sarcophagous, omnivorous = pantophagous, insectivorous = entomophagous, etc. I can't say I've actually heard of any of those Greek forms used in English, but there's no reason they shouldn't be.