An evocatus was a soldier in the Ancient Roman army who had served out his time and obtained an honorable discharge but had voluntarily enlisted again at the invitation of the consul or other commande
Centurion
…Military establishment of the Roman Empire Evocatus, related Roman rank Chiliarch, commander of a thousand…
Statue of Jupiter Dolichenus from Carnuntum, erected by Atilius Primus, an evocatus of the Legio XIV Gemina. The dative form ēvocātō is visible at left.