The desire to link people of the same surname from the same region is strong. After all, how many families with the same surname in a small Portuguese village? The problem is that Portuguese surnames are fluid, they evolve, they come out of thin air (or so it seems). Five children might use five different surnames and only one of them reflects the surname of either parent.
While there are naming patterns that influenced different eras, they are guidelines not mandatory rules. Now, this does not mean that some surnames were not carried down several generations. It’s more like a caution. If you are looking for specific surnames, you may miss the fact that your people didn’t use the same surname as their parents or grandparents.
This chart is one line in my tree. See how the surname evolves? The original surname, Pacheco de Rezendes (or Pacheco de Resendes) dies out very quickly.
(Click to see a larger view)
Want to delve further into the difficulties involved with Portuguese surname research? Read the article: The Danger of Surname Research with Portuguese Ancestry
Dictionaries can help you with surnames especially if your ancestor’s surname appears to be an alcunha (nickname). Learning the meaning of the words may give you insights into why the surname was chosen.