Here's why it's not a common noun:
* Common nouns are general names for people, places, things, or ideas (e.g., dog, city, book, happiness). They are not capitalized unless they start a sentence.
* Verbs are words that describe actions, states of being, or occurrences (e.g., run, sleep, exist, happen).
Let me know if you'd like to know more about parts of speech!