Is a shell a common noun or a proper noun?

The noun 'shell' is a common noun, a general Word for the hard outer part that protects the body of an ocean creature or amphibian; the hard outer covering of a nut or an egg; an object filled with an explosive to be shot from cannon.

A proper noun is the name of a specific person, place, or thing; for example:

• Dr. Grantham M. Shell, Orthopedic Surgeon, Mobile, AL
• Shell Beach, Pismo Beach, CA
• Shell Oil Company

The Word 'shell' is also a verb: shell, shells, shelling, shelled.