You could look at people's last names and their names have changed over time. I was helping someone do the geneology of the Snook family, it turns out they are lesser aristocracy in England at one time, and Snook is derived from Seven Oaks, the property the family was from.
My grandmother's last name is Irwin, which is Scottish, and I think combining illiterate people with bad spellers taking a census, is why there are Irwin, Irvin, Erwin, Irving are all different spellings of the same name. If you go back far enough - say the time of Dal Riata, it was Erinviene, which meant "western noble" or "Irish Lord", since the nobility of southern Scotland at the time were nobles from Ulster settling in Southwestern Scotland. The earliest named person I am aware of from my family geneology is Grim Erinviene who was the first king of Strathclyde (circa 2nd century of the previous millennia). So I guess in reality, my Scottish heritage is really Irish.