What Is a Sin Eater on ‘Outlander’? Season 6 Addresses the Practice

According to outlets like Vice, Gizmodo, and Atlas Obscura, sin eating carried a social stigma. Those who agreed to take on the profession were likely in need of money. Alas, it was widely believed that the sin eater would become worse each time they consumed someone’s sins. As such, they were perceived as the accumulation of the transgressive deeds the parishioners committed during their lifetime.

Source: https://www.distractify.com/p/sin-eater-outlander