What is the origin of the idiom "knock yourself out" and when to use it?

The origin of the idiom "knock yourself out"is not well-documented, but it has been in common use for many years as a friendly way to grant permission or encouragement. It likely developed as a figurative way to encourage someone to enjoy an activity to the fullest without worrying about restrictions or limitations. This phrase is now commonly used to grant permission or express encouragement in a friendly and informal manner.