possibly as a play on Bimmelbahn (“a train with a bell”). <span class="searchmatch">Bummelbahn</span> f (genitive <span class="searchmatch">Bummelbahn</span>, plural Bummelbahnen) (informal) A slow local train. 1905...
Declension of Bahn [feminine] train, railway Achterbahn Bergbahn Breitspurbahn <span class="searchmatch">Bummelbahn</span> Bundesbahn Dampfbahn Drahtseilbahn Einschienenbahn Einspurbahn Eisenbahn...