The mouth is the opening in your face used for eating, drinking, breathing, and speaking. The word can also mean the place where a river flows into a larger body of water.
From Old English *mūþ*, related to German *Mund* and Dutch *mond*. The extended sense for rivers comes from the idea of an opening that lets something flow out.
Your mouth is both a physical tool and a social one: it takes in food and sends out words. The same image works so well that we use it for rivers too—water “speaks” into the sea through a river mouth. Many languages reuse body-part words this way, mapping our bodies onto the landscape.
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