Saint Agnes of Rome, Agnes Bain’s namesake, was a Catholic Saint, martyred at a young age for practicing her faith. After a Roman prefect sentenced her to death, she was to be burned at the stake, but the pyre would not light. She was beheaded instead. While religion does not play a major role in Shuggie Bain, there is an undercurrent of tension between Catholics and Protestants, fueled partially by the ongoing Troubles in nearby Ireland, where the Catholic Irish Republican Army fought for independence from the Protestant United Kingdom. Agnes grew up in a Catholic family and was initially married to the Catholic Brandon McGowan, but she left him for Shug, a Protestant. This was a constant point of tension for Lizzie, Agnes’s mother.

George, the leader of the first Alcoholics Anonymous group Agnes attends, makes the connection between Agnes and Saint Agnes. Agnes’s name spurs George into an impassioned speech, likening the lament of Saint Agnes, “I am on fire. I do not burn” (230) to the suffering of an alcoholic. According to George, like fire, alcoholism burns up all it touches; he says, “Money burns, families burn, careers burn, reputations burn, and then when it's all burned, you still burn” (231).