Insider (noun)

1. A person who has inside information about something, especially in a particular profession or organization.
2. A person who is in a position of power or privilege within an organization.

Origin:

Mid 20th century: from inside + -er.

Examples:

1. The insider had insider knowledge about the company's plans for expansion.
2. The insider was privy to confidential information about the company's finances.
3. The insider was an executive with access to sensitive information.
4. The insider had close ties to top government officials.
5. The insider was a respected member of the community with a wealth of experience and knowledge.