What does Mateo mean?
The Spanish form of Matthew, from the Hebrew Mattityahu, meaning 'gift of Yahweh' (mattan 'gift' + Yah, a name of God). It reached Spanish through the Greek Matthaios and Latin Matthaeus, the name of the apostle and gospel-writer.
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.