The adjective 'common' has two basic meanings according to Oxford:
Occurring, found, or done often; prevalent: ‘common misspellings’
Shared by, coming from, or done by two or more people, groups, or things: ‘the two republics' common border’
What is the exact meaning of the adjective 'common' in the grammar term 'common noun'?
Does the adjective 'common' mean 'found often' or 'shared'?
FYI, 'common noun' is defined in Oxford as follows:
A noun denoting a class of objects or a concept as opposed to a particular individual. Often contrasted with proper noun