What is origin of "all in a days work"

[jongrunner5]

What is meant by all in a days work?

[Quizmonster]

As regards the meaning, it usually relates to something you've done which you wouldn't normally expect to have to do. In other words, people around you are probably surprised that you were even capable of doing such a thing, so different was it from your normal activities. That's when you smile self-deprecatingly and say: "It's all in a day's work", as if it were the sort of thing you do all the time. As to who first used the phrase originally, I'm not sure.