Yeah its weird its a lost skill. Apparently Sepp got the idea from his childhood when a man used to come round the villages making and selling it to people in the villages.
The nearest thing that sound similar here was a product here called renardine which is probably a more refined version but it was banned here in 2005 for seemingly no reason. Since it was first made in 1895 I guess people lost the skill of making it because they bought that instead.
Dippel the alchemist is meant to invented it Dippel's oil which sounds similar to bone sauce. He also invented Prussian blue and seems to be the basis for character Frankenstein.