Iono- comes from the phrase "I dont know". Ever since the Instant Messenger phenomonon, many have become lazy with typing and decided to cut it down from "I dont know ?" to iono?
Lazy people, who are too lazy to type out a complete word on the computer. Never capitlized. I dunno, I don't know. I first hurd the 'word' from my boyfriend online.. and I was like what the f*ck are you saying?!