There are multiple origins and meanings for the name Sebastian:
1. Comes from the ancient Greek word (σεβαστός) [thebathtos] - "high, holy; venerable". The epithet of the Roman emperors
2. Comes from the Latin (Roman) name, meaning - "from Sebastia (Roman Armenian city)"
St. Sebastian was born at Narbonne, Gaul. He became a soldier in the Roman army at Rome in about 283, and encouraged Marcellian and Marcus, under sentence of death, to remain firm in their faith.