Why is your mug your mug?

Question

It's pretty common practice today, most noticeably with the mug shot. Your face is your mug. But what I really want to know is why? Why did the face also become known as a mug and when did it happen?

Answer 1

It is one of those terms whose exact origin is up for debate. One suggestion is that peoples faces were compared to ugly faces on beer mugs which were made with faces modelled on them (Called Toby jugs)

Here is another explanation:
The term derives from mug, an English slang term for face, dating from the 18th century. Another source suggests the term comes from mug, as in grimace, because early subjects would try to reduce their mugshot's value for later identification by grimacing or otherwise twisting their facial muscles (see mugging). This led to the term "mugging" in the acting profession, indicating "emoting" or "overacting", i.e. an amateurish acting performance.