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.