It is a common surname in Spain, particularly in the region of Madrid. It likely originated as a toponymic surname, meaning it was derived from a place name.
The name "Buitrago" itself could refer to:
* Buitrago del Lozoya: A municipality in the Community of Madrid, Spain.
* Buitrago de la Sierra: A municipality in the province of Guadalajara, Spain.
So, while it's not possible to say for certain that someone with the surname Buitrago is definitively Spanish, it is a strong indicator of their Spanish heritage.