Heard it mentioned somewhere a long time ago, don't remember where. I thought it sounded unique enough, so I used it. Since then I have earned plenty of nicknames - Haderade, Chullz (play on my real name), Hater - but everyone still formally knows me by Hader. And despite being told on various sites that "The name Hader is taken", I have never run into anyone with the same name or any different spelling of it.