A paranoidal schizophrenic and a single dev of Temple OS thought thar he's watched and messed with by federal agencies. He knew, because he could see a glowing aura around them undercover agents. After his ramblings about it, 4chan boards users who watched his streams as a lolcow (a person of interest who can be milked for lulz) took this slang term from him. Then it spread everywhere.