Fanatic (noun)

1. A person who is extremely enthusiastic about or devoted to something.
2. A person who is motivated by an excessive or irrational enthusiasm.

Origin:

From the latin word "fanaticus" meaning inspired by a god, frenzied.

Examples:

1. He is a fanatic of football.
2. She is a fanatic of tennis.
3. She became a fanatic of a particular political party.
4. He's a fanatic of technology.
5. She's a fanatic of books.