What is the origin of the idiom "be done for" and when to use it?

The origin of the idiom "be done for" is uncertain, but it may be related to the idea of something being finished or done in the sense of being completely defeated or destroyed. The phrase has been in use in English since at least the early 19th century, and it has been applied to a wide range of situations, including personal and financial struggles, as well as business and political ventures. In general, the phrase is used to describe a situation where there is little hope of success, and where failure is almost certain.