تعریف و معنای "if worst comes to worst"

What is the origin of the idiom "if worst comes to worst" and when to use it?

The idiom "if worst comes to worst" is used to express a situation in which the most unfavorable or extreme outcome is being considered. The origin of this phrase is rooted in the idea that if things deteriorate to the point where the worst-case situation unfolds, one should be prepared to take action.