The earliest surviving text to attach the name Longinus to the soldier is the apocryphal Acts of Pilate, the work also known as the Gospel of Nicodemus, usually dated to the fourth or fifth century. It is in this literature, not in the canonical Gospels, that the lance-bearer acquires a name, and it is here that the piercing soldier and the confessing centurion begin to be fused into a single convert figure.
A striking early witness in art confirms how quickly the name spread: the Rabbula Gospels, a Syriac illuminated manuscript of 586, labels the soldier at the cross LOGINOS in Greek letters, showing the name in settled use by the sixth century.
From these roots the full legend grew in medieval collections such as the Golden Legend: Longinus, whose eyesight was failing, is healed when the blood and water touch his eyes; he believes, abandons soldiering, is instructed by the apostles, and preaches in Cappadocia, where he is martyred. He is venerated as Saint Longinus in the Roman and Eastern calendars.
The atlas states the provenance plainly. The soldier is scriptural but anonymous; the name and the biography are extra-biblical, first attested in the Acts of Pilate tradition, and the martyr-narrative is hagiographical legend rather than history.