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 | Portugal, Philippines, Brazil, Italy, France |
| Fermen | Spain, Philippines, France, Argentina, Peru |
| Ferment | Netherlands, Brazil, France, Israel, United States |