The given name Erik is derived from the Old Norse name Eiríkr (or Eríkr in Eastern Scandinavia due to monophthongization). The first element, ei- is derived either from the older Proto-Norse *aina(z) meaning "one" or "alone" or from Proto-Norse *aiwa(z) meaning "ever" or "eternal". The second element -ríkr derives either from *rík(a)z meaning "ruler" or "prince" (cf. Gothic reiks) or from an even older Proto-Germanic *ríkiaz which meant "powerful" and "rich". The name is thus usually taken to mean "one ruler" or "eternal ruler" or "ever powerful," etc.
The most common spelling in Scandinavia is Erik. In Norway, another form of the name (which has kept the Old Norse diphthong) Eirik is also commonly used. In Finland, the form Erkki is also used. The modern Icelandic version is Eiríkur, while the modern Faroese version is Eirikur. Éric is used in French, and in Germany Eric, Erik and Erich are used.
Although the name was in use in Anglo-Saxon England, its use was reinforced by Scandinavian settlers arriving before the Norman Invasion. It was an uncommon name in England until the Middle Ages, when it gained popularity, and finally became a common name in the 19th century. This was partly because of the publishing of the novel Eric, or, Little by Little by Frederick William Farrer in 1858.
In Norway, Sweden and Finland, the name day for Erik and Eirik is May 18, commemorating the death of Saint Eric of Sweden.
The feminine derivative is Erica or Erika.
Read more about Eric: Fictional Characters