What does Sebastián mean?
The Spanish form of Sebastian, from the Latin Sebastianus 'from the city of Sebaste', whose name derives from the Greek sebastos 'venerable, revered' (the Greek equivalent of the imperial title Augustus). Borne by the early Christian martyr Saint Sebastian.
What does Diego mean?
A Spanish name of genuinely disputed origin. Traditionally explained as a short form of Santiago (Sant-Yago, 'Saint James', from Hebrew Jacob), but many scholars now derive it instead from the Latin Didacus — itself possibly from the Greek didache 'teaching'. The two theories remain unresolved, so any single 'meaning' should be treated with caution.