If you’re reasonably familiar with portuguese names, you’ll notice a lot of them end with “eira”: Pereira (m’wife’s maiden name), Nogueira, Oliveira, for example, and if you’re even more switched on, you’ll know that these, along with a few other names – Carvalho springs to mind – are names of trees*.
It seems as though there’s some doubt over the origin of these names. One theory is that they were adopted by the “Conversos” – Jewish people who converted to Christianity in the late 15th and early 16th century when the inquisition unexpectedly rose to prominence. Doing a little digging, this theory seems to be a bit unsatisfactory. Although a lot of jewish people adopted the names, they already existed before that time, and not all jewish converts chose them either, so… basically, we aren’t much further forward, are we?
While I was looking into this, I found something else that probably should have been obvious: that a lot of names ending in -es such as Nunes, Alvares, Gonçalves and Fernandes were originally patronimics, like Robinson and Robertson. So it wasnt a wasted effort after all.
More here on Wikipedia.
*By the way, can we talk about the fact that “Mangueira” means both “Mango Tree” and “hosepipe”? What sort of well-run language would allow a single word to mean both those things, for heaven’s sake?