It is derived from: "I do not know"
It was changed to: "I don't know"
Then: "I Dunno"
Finally: "Iunno"

Solarpunk is a movement focused on a positive, ecological vision for a future where technology is used for human-centric and ecocentric purposes. It is a literary, artistic and aesthetic sub-genre and is also closely tied to eco-political activism. Solarpunk narratives have a distinctly positive and utopian foundation in contrast to the often dystopian visions found within other "punk" science fiction genres.

I dont know.

another way of saying "i don't know"
often used in online chatting

Conjuntion of "I" and "dunno".

"I dont know", but really fast.
Usually AIM slang.

A phrase most frequently used over the internet. This is a polite way of saying " I don't wanna do what you wanna do , so fuck off . "