Coined by Adam Carolla of Loveline. Combination of "spaz" and "loser". Spaz as in the geek who owns his own comic book store and Loser as in someone who waits outside a studio for an hour and a half for Tia Carrere to sign a copy of Playboy so he can sell it on eBay for $26.
Word stems from the company Nitrous Oxide Systems, or NOS. For some reason ricers call all nitrous oxide systems NOS, even though it's the company name. They didn't create nitrous oxide, "they simply perfected its use and elevated to a position of prominence." Nitrous oxide is written as N2O.