I have just seen this Tanco forum and I was really surprised. Well, it seems that I am the only spaniard in the list, but as you all, I am looking for my family name origins.
Well, first of all, let me introduce myself, my name is Mario Tanco, I am a Telecom Engineer from Malaga (Spain). I have been looking for my roots also for many years without much success I have to admit, I have only little pieces of information that other members of my family have obtained, but which I have not confirmed. Let's see if we can bring some light!
As you all may know, it seems that the origin is in the north of Spain. However from the information we have in our family (which I am trying to confirm), it seems as if these Northern Spain ancestors came from France. There is a rare french name called "Tancogne", which seems to be a reference to a piece of land in the South of France.
My family does not come directly from the north of Spain, but from the middle west of Spain. Overthere there is a region called "Extremadura", where according to my family there are a lot of Tancos. Some are from different families (obviously with a same common ancestor, which indicates that they have been living there for several decades probably). However, I have not found any record about this community nowhere in the web. The mormons database, which I think is the better in the world, does not include a single record of Extremadura. I don't understand why.
Curiously, these two are the two main places where Tancos can be found in Spain. So it does not seem that they spread from the north to the rest of Spain.
It is not clear either when do they crossed the ocean to go to America. My family's theory is that the Tancos from Extremadura participated in the first trips to the new continent after the discovery in the 15th century (Extremadura is the home land of a lot of spaniard conquerors that went to America), but at the moment it is only a theory.
About the reason why the could have moved from France to Extremadura, another family theory is that they came with knight groups after the Spain re-conquer against the muslims in the 15th century. Again, Extremadura was an important settlement of Templar Knights. In fact, I am not wrong the last Templar knight died in Extremadura, in my father's village called Jerez de Los Caballeros ("Jerez of the Knights")
Well, I hope that this will bring a little more excitement to the adventure of finding our roots. It would be great if we could find out where exactly did they come from.