Originally an Anglicized form of the ancient Irish male name Ceallach. It is now very widely used in the English-speaking world, mainly as a girl's name. This is a transferred use of the surname Ó Ceallaigh ‘descendant of Ceallach’.
German: 1. habitational name for someone from Basel in Switzerland (see Besler), or from any of various places called Basse or Bassen in northern Germany. 2. Alternatively, perhaps from a derivative of Middle Low German baseln ‘to act in a confused manner’, hence a nickname for someone who was absent-minded or forgetful.