I read in a magazine that Cargill Inc. is a multi-million dollar business, the biggest privately-owned firm in the USA, and the founder was the son of a Scottish ship's captain called William Dick Cargill. Cargill was always the commonest surname in the fishing village of Auchmithie, near Arbroath, where one line of my family came from, so I thought I would check out Wm. Dick Cargill on Wikipedia.
When I did, I discovered that he was actually born in Orkney on March 12th 1812, the son of a Thomas Cargill and Margaret -. So I had a look for him on Scotlandspeople, and drew a blank. In situations like this I resort to the "fuzzy matching" option to get variants of the surname, and it turned out that our man was actually born William Dick Corrigill, on the date given above, to Thomas Corrigill and Margaret Dick. Presumably someone in the family decided that Cargill would be easier than Corrigill for Americans to get their tongues round.
Many Americans have difficulty tracing their Old World ancestry precisely because an ancestor - or an official at Ellis Island - changed their original surname, hence the popularity of online genetic genealogy forums with so many American family-history researchers.
Harry