Columba (521-597) Irish Celtic missionary. Columba was born in Donegal, Ireland. Very little is known about his early life and education. He studied at Celtic schools, and in 551 was ordained a priest. Later, in 563, at the age of 42, he and 12 of his followers sailed to Scotland, where he established a centre of missionary. activity at Iona. His labours resulted in spreading Christianity throughout the entire island of Britain. The picture left is the abbey of Iona.