I wouldn't say "fabric" for this meaning. There's also surstoff (oxygen) and other expressions where stoff means rather something like "material", or "element".
Since we're talking about slang, older German action movies have "Gib Stoff!" (Give stuff) for "accelerate, the bad guys are coming!".
What you're probably hearing is the difference between how English speakers pronounce R's and how Norwegian speakers pronounce R's. In English we have what we'd call a Common R (postalveolar approximant) but in Norwegian (at least the dialect the Duo voice uses) I believe it's a Tapped R (alveolar flap) or a Rolled R (alveolar trill), which is somewhat similar to the D sound because the tongue hits the same part of your mouth. In fact one way of practicing this kind of R sound is to start by substituting R's with D's and working from there.