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