Saint Kessog was an Irish missionary of the mid-sixth century active in the Lennox area and southern Perthshire. Son of the king of Cashel in Ireland, Kessog is said to have worked miracles, even as a child. He left Ireland and became a missionary bishop in Scotland. Using Monks' Island in Loch Lomond as his headquarters, he evangelized the surrounding area until he was martyred, supposedly at Bandry, where a heap of stones was known as St Kessog's Cairn. He was killed in 520 AD.