My first search in finding the origin of the name Passenheim did not provide any useful information. The only results were there was a town with the name Pasym (German: Passenheim) in East Prussia which after World War II was placed under Polish control. When this occurred, most or all the German people left the town. Since there are no Passenheim families in the town of Passenheim, this first search does not help in finding the origin of the family name Passenheim.
Several years ago, I contacted an ancestry researcher who served as the Public Relations Officer of the Protestant community
for the town of Passenheim. I asked him if he could search the church records and tell me if he finds anything about the
name Passenheim. The amazing thing is, the family name Passenheim does not exist in the parish registers for the town of Passenheim.
On some pages from the Internet, one finds the family name Passenheim is closely related to the East Prussian towns of Königsberg, Stockheim and Abschwangen. These locations are geographically closer to the River Passarge, which is located on the Prussian ridge rising north of Hohenstein and flowing below Braunsberg in the Vistula Lagoon (Frische Haff), then into the City of Passenheim. I suspect that the surname Passenheim was a reference to the River Passarge rather than the East Prussian City of Passenheim.
On the website of Steffan Bruns, he gives some explanations of how names changed over the years. He writes about missing rules and illegible handwriting which led clergy members (churches were often the record keepers of their parishioners) to change the spelling of names. So there easily could have been a change of family names Passenheim and Passarge.
The East Prussian town of Passenheim as an eponym for the family name Passenheim appears to be
a dead end. The idea of the river Passarge as the name giver and then changed to the name
Passenheim is only a presumption. If you have any other ideas of how the family name Passenheim
originated, please contact me.