Its end looks like a navel, which is a bellybutton
lavel
The navel may be infected (called navel ill), or the calf may have a hernia, something which needs to be seen by the vet to be fixed.
a dirty navel
The leftovers from distillation are called "residue" or "distillation residue." This is the material left behind after the desired components have been separated through the distillation process.
a dirty navel
The residue of combustion is called ash.
A seedless orange is called a navel orange. Navel oranges are characterized by the small undeveloped secondary fruit embedded at one end, resembling a human navel. This small fruit is sterile, resulting in seedless varieties.
slag
Residue left on your plate after eating may be called crumbs or scraps by others.
Anti-navel
Your navel