The story of the word monkey begins with a very wily fox.
Reynard the Fox was the hero of a series of stories told long ago in France. The first written-down version, Ysengrimus, by Nivardus de Ghent, came along in about 1150 (just to confuse things further, Ysengrimus was actually the baddy, and a wolf).
One of the characters in the stories of Reynard is Moneke, the son of Martin the Ape - and the story was so popular that moneke soon became a common word for monkey.
The word was probably brought to England, with the stories, by members of a circus.
What a wonderful way to arrive!
Oh, and by the way, brass monkey: it started off cold enough to freeze the toes off a brass monkey. There also used to be another expression hot enough to melt the nose off a brass monkey, too.
Neither of them is anything to do with cannon balls - the physics doesn't work!
Word To Use Today: monkey. Moneke (see above) might have been a pet form of the Portuguese mona (or some similar word), which means female ape.
It might also be connected with the Arabic maimum, which means lucky. If it is then that was just sarcasm, as seeing a monkey was regarded as being about the unluckiest thing you could do!