Meaning of 'knock yourself out'

'Knock yourself out' is an informal idiom that means to give permission or encouragement to someone to do something they want to do. It can also be used sarcastically to dismiss or show indifference towards something. The expression has multiple meanings. Firstly, it can mean to cause oneself to become unconscious, as in getting knocked out in a boxing match. Secondly, it can mean to make oneself very tired by doing work. Lastly, it is mainly used in the US to tell someone to go ahead and do something. It can be used synonymously with phrases like 'go ahead' or 'go for it'. It can also be used sarcastically to express disinterest or dismissal towards someone's idea or request.