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.
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.