What is the origin of the idiom "pull one's leg" and when to use it?

The exact origin of the idiom "pull one's leg" is not well-documented, but it likely originated in the United Kingdom in the late 19th century. The phrase was first used to describe someone joking or teasing another person in a playful or humorous way. The idea behind the expression is that when you pull someone's leg, you are metaphorically playing a light-hearted trick on them, much like a prank or a jest. This expression is used to imply that someone is teasing or joking with another person, often in a good-natured and playful manner. It is a way to suggest that what has been said may not be entirely truthful or that it is meant to be taken with a grain of salt. It is commonly used in informal conversations to lighten the mood or to acknowledge humor.