WTF is bellybutton “lint” and where/what does it do/come from??? 
Over the course of the day, your shirt is abraded against your skin and small fibers from the fabric are pulled off and begin to accumulate. The hairs around your bellybutton happen to do a good job of funneling these bits of fluff into the bellybutton. Shaving the hairs around your navel will reduce lint collection.
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Colibri
General Questions Moderator
Here’s an experiment: Wear a t-shirt with stripes of different colors. Then check to see if the bellybutton lint accumulated when you wear the shirt ends up having corresponding concentric rings.
Absolutely, but the environment you describe is an classic “innie”, which I am.
Have you actually tried the shaving experiment?
Also just curious about “outies”, do they collect any lint?