It indicates that the person's ancestors originated from a specific place or region, similar to the use of "van" in Dutch names or "de" in French names.
For example:
* "Silva" is a common Portuguese last name.
* "De Silva" means "of Silva" or "from Silva". This implies that the person's ancestors were from a place called "Silva" or a region associated with that name.
The "DE" is not always used for all people with the same last name. Some people might use "De" while others might use the last name without the "De". It depends on the family's history and traditions.