Definition & Meaning of "leg to stand on"

What is the origin of the idiom "leg to stand on" and when to use it?

The idiom "leg to stand on" is believed to have originated in the 17th century. It is thought to have come from the practice of dueling, in which a duelist who was wounded or unable to stand was said to have no leg to stand on and was therefore at a disadvantage. This idiomatic expression came to be used to describe someone who had no support or justification for their position or opinion.