What is the origin of the idiom "go in one ear and out the other" and when to use it?

The origin of the idiom "go in one ear and out the other" is rooted in the simple concept of auditory perception. It reflects the idea that when something is heard or spoken to a person, it may enter one ear but not be retained or comprehended and instead quickly exits through the other ear. This idiom has been in use since at least the 19th century. This expression is used to describe a situation where information, advice, or instructions are heard but not absorbed or remembered by the listener.