Kamikorosu. Kamikorosu. That's all you ever heard Hibari Kyoya, Head Prefect of Namimori-Chuu's Disciplinary Committee, say; seldom did any words come out of his mouth that didn't involve kamikorosu or pointing out that you were crowding like a pack of herbivores. It was questionable about how, where and why Hibari Kyoya had picked up his infamous kamikorosu phrase. Of course, no one dare ask him, yet...

Like most young boys, Hibari enjoyed reading manga, or comics. When he was a boy - say around six or so and was learning to read - he would read this one particular manga series which no one liked at all back in those days. It was a gag manga - published in a shounen company's magazine every week. Young Hibari would steal into the store every week and read the manga from the magazine - never missing an issue. And in that manga is where he found kamikorosu. The main antagonist bad guy spoke it often. He would shout to the protagonist "Kamikorosu!" whenever they engaged in battle.

Keeping in mind that Hibari was still a young boy, he of course found the phrase to sound "cool."
"Kamikorosu!" He'd mutter under his breath at people whenever he was angry with them (which was mostly always). Until he eventually started speaking it out loud, and at people directly.
The gag manga was soon canceled shortly after, and since no one ever read it save Hibari himself, they could not guess where this Hibari Kyoya kid had learned such a phrase from. Maybe he made it up himself - kids' imaginations and all. But soon, his kamikorosu was known to every citizen of Namimori.

Some laughed at him for its ridiculous-ness - adults that is. While some feared him whenever he spoke it with his little angry glare - the other kids that is. Hibari was someone to kamikorosu you if you didn't let him score a point while playing any sport. Not that it mattered, since Hibari didn't like to play with the other children. Even being a teenager today now he still used the phrase. Constantly. Apparently, it still sounded "cool" to him. After all those years... clearly, this person never truly changed.

And so, what about herbivore? Had Hibari Kyoya gotten an idea to address people as such from somewhere? Or had he simply grown into using it by his misanthropic ways for people? Whatever the case... no one dare ask him.

I can so see Kyoya liking a manga which no one else would like - like a lame gag one. Like with the lame school song. XP