Thomas is commonly known as "Doubting Thomas" because he initially doubted the resurrection of Jesus Christ when he was told of it (as is related in the Gospel of John); he later confessed his faith ("My lord and my God") on seeing the places where the wounds had healed on the holy body of Jesus after the Crucifixion of Jesus. While it is often assumed he touched the wounds in art and poetry, the scriptures do not say that he touched the wounds.
–Wikipedia