grinden

Right ! Okay...I will have to do some searching :)

ok, not 100% sure on this, but:

"Yegelich dbeste, dat zi konden, Van den ritter us gegronden,"

From [[1]], this is a use im Middle Dutch of the past participle ?

It's a strong participle so I don't know what else it could be. The text itself looks pretty odd though, it has a lot of High German stuff thrown in. The spelling is Dutch, but the phonology and grammar look more German. So I'm not sure if it can really be considered Middle Dutch as such.