Holy Lance
The name of the soldier who pierced Christ's side with a "lonchē" is not given in the Gospel of John, but in the oldest known references to the legend, the apocryphal Gospel of Nicodemus appended to late manuscripts of the 4th century "Acts of Pilate", the soldier is identified as a centurion and called Longinus (making the spear's Latin name "Lancea Longini").
Commemoration of the Passion of Christ
Whilst the feast in honour of the instruments of Christ's Passion—the Holy Cross, Lance, Nails, and Crown of Thorns—called "Arma Christi", originated during the Middle Ages, this commemoration is of more recent origin. It appears for the first time in the Breviary of Meissen (1517) as a "festum simplex" for 15 November. The same Breviary has a feast of the Holy Face for 15 January and of the Holy Name for 15 March.