von or vom?

Rok vom Wheeler Kloppenburg

Just Bark at it.-
Barked: Fri May 16, '08 2:13am PST 
I am curious about the use of vom or von in the name. I thought it might have something to do with gender, but both Rok's parents use vom, so I did the same. I know von means of, such as from a certain breeder and vom also means of but as in 15th of May. Hope I named him correctly.