Family name Trehn (Trehn 
) , in all the world, is a very rare cognomen. The family name Trehn is habitual in Sweden, where it is a rare surname, Italy, where it is an extremely rare surname, and India. Much less frequently, Trehn is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Trehn | Sweden, India, Italy, United States |