تعریف و معنای "[fall] on {one's} sword"

What is the origin of the idiom "fall on one's sword" and when to use it?

The idiom "fall on one's sword" comes from ancient Roman times, where a defeated or disgraced leader would commit suicide by falling on their sword. It has been in use in English since at least the 17th century. It is used to describe a situation where someone takes responsibility for a problem or failure, often at great personal cost.