tl;dr: The Christian saints Barlaam and Josaphat, venerated by Catholic and Orthodox churches, are actually a retelling of the Buddha's life story, transmitted via Sanskrit ("Bodhisattva") through Persian, Arabic, and Georgian versions before entering the Christian tradition in the 10th century. The name "Josaphat" itself derives from "Bodhisattva," and though scholars had noted parallels for centuries, the Buddhist origin wasn't widely acknowledged until the mid-19th century. The tale illustrates how religious traditions have long absorbed and reinterpreted each other's stories across cultures.