The popular etymology of the town's name derives it from the River Penk, which flows through it. It was assumed that since the town could be said to stand on a ridge by the Penk, it must derive its name from the river. However, this is to reverse the true derivation. The name of the town, or something like it, is attested many centuries before that of the river. The name "Penk" is actually a back-formation from the name of the town.