The mark or indentation on the abdomen where the umbilical cord was attached before birth; also called a navel.
From 'belly' (stomach area) plus 'button' (because of its small, rounded appearance). A simple compound word that describes the thing by its location and appearance.
Every mammal has a belly button—it's the scar from being connected to their mother! Human bellybuttons vary wildly (innie vs. outie), but we all have this universal mark of where we started life.
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