[quote=Rin]
It's... A very commonly used word in anime fandom, actually. Has been for years. It's a play on the even more commonly used "tsundere".
[/quote]

uhhhhhh guys?

Yandere and Tsundere aren't "Commonly used terms" or "Plays" on each other. Yandere and Tsundere translate directly into something like Possessive Love and Violent Love respectively. I don't know the actual translations but they're not just sayings, they're real japanese words.