Wet behind the ears

What is the origin and meaning of the phrase "wet behind the ears"?

Meaning: Very gulible or innocent

Origin: The 'wetness' is suposed to be from just being born. Ie. you still have the fluid from your mothers womb behind your ears.

If someone is wet behind the ears they are regarded as being inexperienced and new to a task. The saying is many hundred of years old and comes from the fact that many animals, when they are new born, have a small depression behind the ears. The young themselves are wet at birth and this depression is the last thing to dry out. By the time it does, the animal is a little older and possibly wiser.