What is the origin of the idiom "in the dark" and when to use it?

The idiom "in the dark" dates back to the late 1600s and has its roots in the idea that darkness represents ignorance or lack of knowledge. Just as you can't see in the dark, being "in the dark" means being uninformed or unaware of something. This expression is used to describe a situation in which someone lacks information or knowledge about a particular subject, event, or circumstance. It implies a state of ignorance or being kept unaware intentionally or unintentionally.