Austria of 1847 was entirely different than modern day Austria. The territory of Austria-Hungary included all or part of the modern countries of Austria, Hungary, Czech Republic, Poland, Ukraine, Slovakia, Serbia, Slovenia, Italy, Croatia, Bosnia, Montenegro and Roumania. That old Empire had many official languages.

Do know the language they spoke?

What was their religion?

These 2 questions may help answer your question... there is no place called Bonemis, now nor then.

Could it have been Bohemia? This is now the Czech Republic.

However checking US immigration records I find numerous TOPIC (which is found in Croatia name) coming from a place called Brocanac

You need to know the exact place they originated in order to begin a search.....

Robert Jerin
Croatian Heritage Museum
Cleveland Ohio