Knock yourself out is an idiom that came into use in the twentieth century. We will examine the meaning of the idiom knock yourself out, where it came from, and some examples of its use in sentences.
To knock yourself out means to exert maximum effort, to try as hard as you can to achieve a goal. This is the original definition of the idiom, which came into use in the 1930s. The idea is that one is trying so hard to achieve something or is working at maximum capacity to the point of injuring one’s health. However, the idiom knock yourself out took an additional meaning in the latter-1900s. Knock yourself out is now also often used to give someone permission to proceed or to attempt to accomplish something.
By all means work hard but don’t knock yourself out trying to do things that are clearly beyond your capabilities. (The Globe and Mail)
But don’t knock yourself out trying to tie a size 28 bug to hair-thin 7X tippet with frozen fingers. (Field and Stream Magazine)
If selling Chris Nolan’s The Prestige as a fantasy about a good magician (Hugh Jackman) facing off against an evil magician (Christian Bale) who might be an actual wizard gets you that opening weekend, knock yourself out. (Forbes Magazine)
So, knock yourself out if you want to look like a model. (The Sydney Morning Herald)