Quick answer
Ceallach is a boy name meaning "bright-headed; war, strife; church".
Meaning and history
From Old Irish Cellach, of uncertain origin, traditionally said to mean "bright-headed". Alternatively it could be derived from Old Irish cellach "war, strife" or cell "church". This name was borne by several early Irish kings and by a 12th-century saint, an archbishop of Armagh.
Notes and context
Usage: irish