Erin is a Hiberno-English derivative of the Irish word "Éirinn". ("Éirinn" is the dative case of the Irish word for Ireland - "Éireann").

According to Irish mythology and folklore, the name was originally given to the island by the Milesians after the goddess Ériu.

Poets and nineteenth-century Irish nationalists used Erin in English as a romantic name for Ireland. In this context, along with Hibernia, Erin is the name sometimes given to the female personification of Ireland.

Erin go bragh ("Éirinn go brách" in standard orthography), a slogan dating from the 1798 revolution, is often translated as "Ireland forever". The etymological history of the word as it drifted throughout the Gaelic region gave rise to its use by the early Scots to both mean Ireland and "west" - as Ireland lies to the west of Scotland.

As a given name, Erin is used for both sexes. Although, given its origins, it is principally used as a female name. It first became a popular given name in the United States.Fact: date=September 2008 Erin is also a name for Ireland in Welsh, and is one of the top 20 most popular girls' names in Wales.

As a family name, Erin has been used as one of the many spellings of the name of the Scottish clan "Irwin" - which was involved in the Scottish Plantations of Ireland. However, their name was originally derived from the place of the same name near Dumfries, and means "green water", from Brittonic ir afon.