I'm not an expert in Icelandic orthography, but the general case is "<name>'s son/daughter", e.g. "son of Fredrik" -> Fredriksson and for <name> ending in "s",

I'm not an expert in Icelandic orthography, but the general case is "<name>'s son/daughter", e.g. "son of Fredrik" -> Fredriksson and for <name> ending in "s", I knew "son of Magnús" -> Magnússon. But I should've checked, because I've looked it up now, and "daughter of Magnús" should be Magnúsdóttir. So we'd get Travisson / Travisdóttir.