Intimate means being close. A small restaurant is called intimate because you're sitting close to the other people, and your best friends are considered your intimate friends.
This adjective can mean very friendly, or very personal or private. The original spelling was intime, from French, from Latin intimus "innermost," from intus "within." The related verb intimate means to hint or suggest. Intimate is also a noun meaning a close friend or associate. You might intimate to your intimates that you want to leave a boring party.