What is the origin of the idiom "know something backward and forward" and when to use it?

The idiom "backward and forward" is an extension of the idiom "know something back to front." In this case, it emphasizes a more comprehensive understanding by suggesting that one knows every aspect of the subject so well that they can navigate it as easily backward as they can forward. This expression is used to describe an in-depth and complete understanding of a subject, task, or situation. It implies that the person is so familiar with it that they can handle it effortlessly, both forwards and backwards. It can be applied in various contexts, such as work, hobbies, or expertise in a particular area.