You are totally correct about the conversos
(I only know the Spanish term, sorry!)...the arrogance of the Church was unbelievable.
I think Silva means "woods", Alex, as in "a collection of trees" or "forest". The Latin version gives us the female name "Sylvia" and the English word "sylvan", meaning "wooded".
It's like the difference between "floresta", "madeiras" and "arbusto" in Portuguese: forest, woods, bush.
In Canadian and Australian English, however, an uncleared forest, or a forest that is regrowing after being cut down is commonly called "the bush", as in "Tim is out in the bush trying to bag a deer". (You would hear that a lot in Saskatchewan...they have a great deal of "bush" there.
My kid plays with another boy called "Silva" and it's a ridiculously common name, like "Smith" in English. I think those ex-Jews had many children in order to be super Catholics.
I wouldn't want you to end up calling the American President "Silva" by mistake....