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. And when you get intimate with someone, it can mean that you're sexually involved.