Is herd a proper noun or common noun?

The noun 'herd' is a common noun, a general Word for a herd of any kind.

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

• Herd, KY 40486
• Herd Street Post Office & Telegraph Building, Wellington, NZ
• The Herd Collection (jewelery), Cleveland, TN

The Word 'herd' is also a verb: herd, herds, herding, herded.