Kessog was a saint of the Celtic Church. His feast day is March 10, in remembrance of his death in the year 520.
Kessog's story begins in Ireland, where he was born of a royal family in Munster. He is said to have performed miracles from an early age (childhood). He undertook religious training with Saint Machaloi while in Ireland, then was sent as a missionary to Lennox in what was Strathclyde, at the time. Strathclyde bordered three kingdoms, Dal Riata (Scots -west), Picts (East), and Welsh (south).
Kessog moved to Luss in the 6th century, building a monastery there on Inchtavannoch (Monk's Island) in Loch Lomond. Kessog was killed at Bandry. His assailants are unknown.
Walter Scott's "The Lady of the Lake" is set in the Trossachs region, Loch Katrine being an inspiration. Loch Lomond, Lennox, Luss - all figure in this poem:
"...The terror of Loch Lomond's side,
Would, at my suit, thou know'st, delay
A Lennox foray--for a day.'--
Proudly our pibroch has thrilled in Glen Fruin,
And Bannochar's groans to our slogan replied;
Glen Luss and Ross-dhu, they are smoking in ruin,
And the best of Loch Lomond lie dead on her side.
Widow and Saxon maid
Long shall lament our raid,
Think of Clan-Alpine with fear and with woe;
Lennox and Leven-glen
Shake when they hear again,
'Roderigh Vich Alpine dhu, ho! ieroe!'..."