Forum:Janos SLYNT

Why did Janos Slynt have a surname before House Slynt was established?

I though it was only trueborns from noble or knightly houses who were entitled to a surname. Also bastards from such houses as well (Snow, Rivers, Hill, etc.).

But before House Slynt was established Janos Slynt was just a commoner (smallfolk), so why did he have a surname?

Thanks.