تعریف و معنای "[know] {sth} like the back of {one's} hand"

What is the origin of the idiom "know something like the back of one's hand" and when to use it?

The idiom "know something like the back of one's hand" suggests that someone is intimately familiar with a subject or topic, just as they are with the physical features of their own hand. It implies a deep and thorough knowledge of the subject. This expression is used to emphasize how well someone knows or understands something, indicating a high level of familiarity and expertise.