where does wet behind the ears come from
Wet behind the ears. Naive. The allusion is to the inexperience of a baby, so recently born as to be still wet. This phrase was in circulation in the USA in the early 20th century - twenty years before it was first recorded elsewhere. The converse of the phrase - 'dry back of the ears', was also known in the USA from around the same date. There is not much in the matter so far as the organ [the courthouse record] is concerned except it is so new that it is wet behind the ears yet.