Evelynn

Why in the world does her name have two N's in it?

It's something that just bugs me. Was this a mistake, or was it intentional?

Evelyn is a name in the English language, where it can be used as a first name or a surname. As a first name, it can refer to persons of either sex, although it is more commonly borne by females. The name originally was used a surname, which derived from Aveline, a feminine Norman French diminutive of the name Ava. Evelyn is also sometimes used as an Anglicisation of the Irish or Aibhilín and Éibhleann.[1] Aibhilín is a variant form of Eibhlín, which is also derived from the Norman French Aveline.[2] Éibhleann, on the other hand, is said to be derived from the Old Irish óiph, which means "radiance", "beauty"; a variant of this name is Éibhliu, another Anglicised form of the name is Evilin. Another school of thought is that the name "Evelyn" means "hazelnut".[3] Variant forms of the feminine first name Evelyn include: Evelyne, Eveline, Evaline, Evylen, Eveleen.[1]