In Ascension canon, Cailan’s name basically means ‘Descendant of Calenhad’ in the old Alamarri tongue. 

He got his name because his parents wanted to solidify, as firmly as possible, that he was, indeed Calenhad’s heir and the rightful future king of Ferelden.

In Ascension canon, Alistair’s name means ‘Defender of men’. But neither Fiona, or Duncan, who picked his name knew that. 

He got his name because Fiona didn’t know any Fereldan names. She let Duncan, who was half-Fereldan name him. Duncan named him after a dog a neighbor had when he was a child.