"Linguistically, Friesian is in the same family as Middle English, while Dutch is a Germanic language. That explains why Peter's verses would be understandable in Scotland, and maybe not so much in the Netherlands". (KathWestra)

Friesian, Dutch, English are all Germanic or Teutonic languages and as such Peter's verses would be understood in Scotland AND in the Netherlands. I remember cycling in the Netherlands with Geordie McIntyre sometime in the late 50's when we/I could hold a limited conversation with a Dutch family who invited us in for tea. It has been said that if James the sixth had kept his court in Scotland then our langauge would be similar to Friesian ... maybe an exageration, but pertinant to this thread.