Do you really think you know it better than a Chinese? Read this:
BBC News - Why China's currency has two names.
Why China's currency has two names:
Jiao and mao
As it happens, Chinese people rarely talk about renminbi or yuan.
100 yuan notes A fistful of kuai
The word they use is "kuai", which literally means "piece", and is the word used historically for coins made of silver or copper.
Also common is "10 kuai qian", literally "10 pieces of money".
"Kuai" is colloquial, like "quid" in the UK and "buck" in the US, but it is the word used in everyday Mandarin, whether you are in Beijing or Taiwan - which, of course, has its own currency, the new Taiwanese dollar, also known as the yuan.
The same thing happens again when you break down your yuan into smaller units, the jiao and the fen (one yuan is equal to 10 jiao and one jiao is equal to 10 fen).
There is nothing wrong with the word jiao, it is just that most people use the word mao instead.
Anyone suspecting a link between the mao and Chinese former communist leader Mao Zedong would be mistaken.
The character is the same as Mao's surname, but the word was used long before he came to prominence.
hmm, lets see what the back of this 5 Jiao note I got says...
It says Wu Jiao, so it must be a Jiao? When they put Mao on it let me know.