Hear no Evil, See no Evil, Speak no Evil Monkeys

What is the origin of these monkeys–is it a custom from India?

IIRC, they originated in Japan.
[useless trivia] Their names are:
Mizaru - See no evil
Mikazaru - Hear no evil
Mazaru - Speak no evil
[/useless trivia]

Ohh! I thought you were talking about that shirt, Hear no Evil, Speak No evil, and Pick your Nose…

What does/do it/then mean, anyway. The real ones I mean.