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.
-- Anonymous User 1/4/2006
Kiefer Sutherland played a character named Nelson in the film Flatliners.
Nelson Mandela comes to mind, but the name also makes me think of the bully on the Simpsons. I'm sure many people would be tempted to throw in a ''ha ha'' when hearing this is someone's name. I don't really like this as a first name, and it doesn't sound very pleasant.