1
general::
Phrase(s): wet behind the ears [and] not dry behind the ears; hardly dry behind the ears
Fig. young and inexperienced. • John’s too young to take on a job like this! He’s still wet behind the ears! • He may be wet behind the ears, but he’s well-trained and totally competent. • Tom is going into business by himself ? Why, he’s hardly dry behind the ears.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, not dry behind the ears. Immature, inexperienced, as in How can you take instructions from Tom? He's still wet behind the ears, or Jane's not dry behind the ears yet. This term alludes to the fact that the last place to dry in a newborn colt or calf is the indentation behind its ears. [Early 1900s]
American Heritage Idioms