The Serbian word dupe/дупе is pronounced doo'-peh, means arse ( jennarenn, dontcry Dupa, pterodactyl) and the first vowel is of medium length - better late than never! - but in this series of comments appears to have been confused with dupa. According to my late wife it was regarded as a giggle word by children in the 1940s in Belgrade, to whom is was no more reprehensible an expression than bum or bottom.
I may have spelled this wrong. I can't seem to find a correct spelling. I first saw this on my grandmother's shelf in the form of a ginghamed jar filled with puckered stocking-ends of various flesh-tones made to resemble posteriors. It was labeled, as I recall, "Pickled Dupas"