The origin of this word comes from the movie "Scott Pilgrim vs The World." A young girl Scott Pilgrim dated. He was 22 and she was 17. Later she worked hard to win him back.
More then one meaning
1. Another name for a girl younger then yourself that you are interested in. (Best used if you don't know their name)
2. A clingy, obsessed, younger chick.
Ex.1 "That girl over there is my Knives Chau"
Ex.2 "Wow * friends name*, *girl's name* is being such a Knives Chau. She even followed me to my class."