knoppern means A kind of gall (blister on a plant) produced by a gallfly on the cup of an acorn, and formerly used in tanning and dyeing. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
Compare German Knopper. See knop.
noun
- A kind of gall (blister on a plant) produced by a gallfly on the cup of an acorn, and formerly used in tanning and dyeing.