grinden

It has no entry, but it's mentioned here [[1]] @ grind_1. A Google search for "grinden" "grond" "gegronden" also turns up a bit more (talk) 23:26, 20 May 2017 (UTC)

Ok, but for it to have a Middle Dutch entry, it would need at least one attestation. For modern Dutch, it needs three.

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.