Conversation so far:
where does my last name garcia come from
Garcia was possibly a Basque surname called Gaztea, and later was Castilianized, into the medieval Kingdom of Castile, becoming García.
Where was the Kingdom of Castile located?
The Kingdom of Castile was a large and powerful state located on the Iberian Peninsula during the Middle Ages.

Question: What was spoken in the kingdom?
Self-contained rewrite: What language was spoken in the Kingdom of Castile?