What does Santiago mean?
A contraction of 'Sant Yago' — Saint James. Yago (also Iago) is the old Spanish form of Jacobo/James, from the Hebrew Ya'aqov (Jacob). The name honors Santiago the Apostle, patron saint of Spain, whose shrine is at Santiago de Compostela.
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.