An Old Drinking Toast Chin Chin

Factual Questions
1

I heard this spoken the other day in an old movie. Everyone raised their drinking glasses in a toast and said “Chin Chin”.

Where does the toast Chin Chin come from and
What does it mean?

Thanks,
Jannal

2

From the OED

3

In Italian, where it is the standard toast, “cin cin”

4

I read somewhere that “chin chin” is a slang term for the penis in Japan (or was it Korea?). I remembered this because our family dog when I was a kid was named Chin-Chin. We had no idea.

5

My dictionary says it is of 18th-century origin in English, and is derived “from Chinese (Peking) ch’ing-ch’ing: please please”.

Presumably this was said when offering food or drink.