Callahan

Irish: reduced Anglicized form of Gaelic Ó Ceallacháin ‘descendant of Ceallachán’, a diminutive of the personal name Ceallach, possibly meaning ‘lover of churches’, from ceall ‘church’, or (more likely) ‘bright-headed’, from cen ‘head’ + lach ‘light’. This name was borne by a 10th-century king of Munster, from whom many present-day bearers of the surname claim descent.