Combination of "
Pringles" and "
dingleberry," describing the discovery of ancient Pringles crumbs that fell into your belly button at least a fortnight ago, and which, over
time, have hardened around one or more of your belly-button hair follicles.
The ensuing fermentation of said pringleberry leads to a related situation called "belly-button hands," which describe a smell associated with rummaging around your belly button whilst fiddling with said pringleberries.