The name Cathal is a boy's name of Irish origin meaning "battle rule". Cathal and is often added to lists like Unique Baby Names: Unusual and Rare and discussed in our forums with posts like "Quick Question Thread?!".
From the experts:
The name of an ancient Irish saint is in the contemporary Irish Top 50. While it's one of the rare Irish names for boys that hasn't immigrated to the U.S., it may follow brothers Aidan and Declan to our shores. The t is not pronounced.