We ordered it anyway, as we were partial to dumplings and to sauerkraut. While waiting for our food to arrive and I looked online, and this entry from Wikipedia popped up, under the topic of Rendering (animal products):
"One edible product is greaves, which is the unmeltable residue left after animal fat has been rendered. An alternative process cooks slaughterhouse offal to produce a thick, lumpy "stew" which is then sold to the pet food industry to be used principally as tinned cat and dog foods."
The dumplings, when they arrived, were very tasty and by then we remembered grammeln from our previous trips. These are the Austrian version of pork scratchings or pork rinds, often served as snacks with wine.
The dumplings themselves reminded us of Cantonese char siu pau, or pork buns, as you can see from the picture below (grammelknödel on the left, char siu pau on the right).
We bought some grammeln later in the supermarket. They were slightly crunchy, but not hard like English scratchings, and very tasty.
You can also get them mixed in with lard to spread on bread. It used to be thought that this sort of thing was very bad for you, but there is some recent research which suggests that animal fats might be OK after all. Not everyone accepts this, but I think I might, while I'm abroad.