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’.
Northeastern English: 1. from the Middle English personal name Almund, from Old English Æðelmund, ‘noble protection’. 2. variant of Allman ‘German’, assimilated by folk etymology to the vocabulary word denoting the tree.