Word to mean unwise/foolish coming from the idea of being untravelled? I remember reading somewhere that there is a word in old Norse for unwise/foolish that etymologically refers to someone who's not travelled or left home. Any ideas?

You are probably thinking of Icelandic _heimskur_ "stupid, foolish", which comes from Old Norse _heimskr_ "foolish, silly; who has never been from home" (from ON _heima_ "home"). It appears frequently in Norse sagas, sometimes in the intensive form _allheimskr_ "very stupid". A famous instance of this is the saying _" Engi er allheimskr, ef þegja má"_ ("No one is a total fool, if one knows when to be silent") in the _Saga of Grettir the Strong_.

I am not aware of an opposite word relating wisdom with being well-travelled, though.