Last name Fermen (Firmo 
, Fermen 
, Ferment 
) , worldwide, is a common surname. The cognomen Fermen is habitual in Portugal, where it is quite a rare surname, Brazil, and France. Very seldom, Fermen is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Firmo | France, Philippines, Portugal, Italy, Brazil |
| Fermen | Argentina, Spain, France, Philippines, Peru |
| Ferment | United States, France, Israel, Netherlands, Brazil |