Nelson

Nelson comes from the name Nielsen which means son of Niel. It was a Scandinavian tradition that one's last name be your father's name with sen (sen means son) on the end. When immigrants came to American, the i was dropped and the second e was changed to an o to Americanize the name.

Well, not quite accurate for all Scandinavian languages. In Swedish -son names are spelled with an 'o', son is the same word in Swedish. Usually Swedish son-names are spelled with two s's though, which they aren't in English. Andersson = Anders' son.