What is the origin of the idiom "a drop in the bucket" and when to use it?

The idiom "a drop in the bucket" has its origins in biblical language and can be traced back to the King James Version of the Bible. It appears in the Book of Isaiah, Chapter 40, Verse 15, where it is used metaphorically to describe something insignificant in comparison to a larger quantity. This phrase is used to describe something that is very small or insignificant when compared to the larger context or quantity it is a part of.