Didymus

Didymus is the Greek word for twin, used in the Gospel of John as an alternative name for the apostle Thomas (John 11:16; 20:24; 21:2). The designation indicates that Thomas's Aramaic name—Tʾōmā, meaning twin—was rendered into Greek for the benefit of wider readers, with both names presented as equivalents. Why Thomas bore this epithet is unexplained in the biblical text; whether he had an actual twin sibling or the name was applied for other reasons is unknown.

Thomas is best known for his absence when the risen Christ first appeared to the disciples, his subsequent profession of doubt, and his dramatic confession upon seeing Jesus eight days later: "My Lord and my God!" (John 20:28)—one of the most direct Christological declarations in the Gospels. Early Christian tradition, unverified in the New Testament, credits Thomas with bringing the gospel to India, where communities bearing his name persist.