Why "Rimpau"?

In several episodes, Bob's office is said to be in the Rimpau Building. Was there an actual building by that name in Chicago at the time? The real-life building they showed in the exterior shots is said to be at 430 N. Michigan Avenue, and one website says it's now called the Charles Schwab Building, but doesn't say what it was called back then.

I really have no idea whether "Rimpau" was ever the building's real name, but if it wasn't then how did it come to be called that in the show? It's a German surname, and the main US branch of the family is on the west coast, primarily in southern California. Considering where Hollywood is, I thought maybe there was someone named Rimpau connected with the Bob Newhart Show. However IMDb lists a total of only 5 Rimpaus, and none of them are credited with anything to do with the show.

I could understand if they'd called it the "Smith Building" or something generic like that. But why Rimpau, considering that there seem to be very few (if any) actual people with that name in the Chicago area?