Well, on topic again (5ºC but sunny and dry, thank Goddess),
BetterRed was right with García
It was a name at Middle Age, but now it's always a surname. If we're talking about Spanish names, in general, forget middle, last name or given name. Spanish names usually are two surnames (father and mother's first surname, mother doesn't lose her surnames after marriage) and the others are name. There're exceptions, of course (Pedro Antonio de Alarcón has two names (Pedro and Antonio), one surname (Alarcón) and "de" is a nexus, as Van or Von.