When my German grandma wanted everyone to stop talking (arguing really) and change the subject at the dinner table, she used a German word that sounded like oompsdaggon. She said it meant change the subject or swap the cars in German. Would anyone out there know this word?
She probably said umsteigen ([ˈʊmˌʃtaɪ̯ɡən] ↔ oompsdaggon), but that’s merely a guess.
There’s no specific translation, but regarding trains, for instance, umsteigen means “change trains”. You also use it when referring to cars.
So she probably encouraged the animated discussion to change subject, to switch to other topics.
While your grandmother surely knew how to baffle the table round, I don’t think it’s a German saying. An established phrase is Lass uns das Thema wechseln, simply meaning “Let’s change subject”.