Eric -- the all-time most popular Scandinavian boys' name in the U. S. -- peaked in the Ricky Nelson/Rick Springfield period. It was adopted by English speakers in the mid-nineteenth century, who were already familiar with the exploits of the tenth century Viking navigator and discoverer of Greenland, Eric the Red.
From the mid-sixties to the late eighties, Eric was on the Top 25 list, and is still at Number 142. Some of its best known bearers: Eric Clapton, Eric Idle, Eric Dane and major characters in The Little Mermaid>, True Blood and Friday Night Lights, not to mention Eric Cartman on South Park. Simon Cowell named his first son Eric after his father.
Erik is the Old World spelling of Eric, now mega popular in Germany and Sweden.