What is the origin of the idiom "wet behind the ears" and when to use it?

The idiom "wet behind the ears" is believed to have originated from the fact that newborn animals, including humans, are born wet and slightly damp behind their ears. This area tends to dry quickly after birth. The phrase has been used metaphorically to describe someone who is inexperienced or naive, much like a newborn who is new to the world.This expression is used to refer to someone, often a young person, who lacks experience or sophistication in a particular area. It suggests that the individual is still learning and has not yet gained the wisdom or knowledge associated with more seasoned individuals.