What is the origin of the idiom "deaf as a post" and when to use it?

The expression 'deaf as a post' is a figurative idiom that originated from the comparison to a post, an inanimate object incapable of auditory perception. This comparison emphasizes the extreme level of deafness being conveyed and is used to describe someone with significant hearing impairment or complete inability to hear. The phrase 'deaf as a post' is considered old-fashioned in its usage and, while still understood by some, is not commonly used in modern everyday conversations.