It was a very smart decision to name one of their main characters after the Saint/Apostle Bartholomew, a skeptic and honest person, whose cause of death was said to be by flaying; a slow form of torture while still being alive, his skin getting stripped off.
Assuming he was outed by his father as it was implied, the Saint's death could be a metaphor related to what it felt like to him; stripped off of his skin, for the world to see what truly lies underneath it. Barth under others' scrutinizing gazes, getting called names, getting bullied, feeling othered, like he doesn't belong. Having no one by his side; a slow form of torture in life itself.
I would also like to point out that St. Bartholomew, who's often referred to as Nathanael as well, is closely linked to St. Philip; the assumptions are that they were dear friends and it was Philip who told and brought Bartholomew to meet Jesus.
I wonder if there's also some kind of link here to Barth and Tanrak's first meeting and eventual relationship.