Ok, I’m not Polish (hopefully somebody Polish will chime in soon) but from neighbouring Slavic country so tried to figure this out with some translator help. My gues it’s something like “tam idzje” (or close to it, might not be comoletely gramatically correct), but pretty butchered - I understand your father doesn’t speak the language but probably heard someone in family as a kid say it and tried his best to mimic them? I’d expect it not sounding quite right.

I think I can get reasonably close to pronouncing “tam idzje” weirdly enough for it to sound something like “yadja”.