It is a patronymic surname, meaning it is derived from a male ancestor's given name. The name likely originated from someone who was born in or came from Galicia.
There are also variations of the name, such as:
* Gallego: This is a common variant of the name, often used as a given name as well.
* Galleguillos: This is a diminutive form of the surname.
* Gallegosa: This is the feminine form of the surname.
It is a common surname in Spain, Latin America, and the United States.