Of all the regions in Germany, the surname "
Päffgen" actually occurs most frequently in North Rhine-Westphalia. The same is true for surnames like "Röttgen", "Schiffgen", "Schnütgen", "Stütgens".
I would also interpret the ending "-gen" as the Ripuarian version of the diminutive "-chen", pronounced [jən]. In the Ripuarian dialect, however, the "Pfaffe" (pastor) would be spelled and pronounced "
Paaf" with a long "a". In the case of the surname with diminutive, however, a shortening would also be possible. The family name also exists in the spelling with only one "f". But I doubt that it would be pronounced with a long "ä" in this case.
The surname "
Paff", whose etymon probably does indeed go back to "Pfaffe" (pastor), is most common in Hessen, but NRW is already in second place.