Her name Regan comes from family name Regan is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to originate in ancient gaelic from ri "sovereign, king" and the diminutive -in, "the king's child", transliterating as "little king".
Her name Regan was derived from the Old Norse regn, ragn (judgment, decision). In Norse legend, Regin, a very wise man, was appointed tutor and foster father of Sigurd or Possibly derived from ríodhgach meaning "impulsive".