thicket

Thicket comes from Middle English thikket, from Old English þiccet, which was built from þicce ("thick") plus the nominal suffix -et. That suffix turned an adjective describing density into a noun for a dense place.

It's stayed a straightforward word for a dense growth of bushes or trees since Old English times.

German Dickicht is a close parallel formation, though it's first recorded much later, in the 17th century — a reminder that languages can independently build the same kind of word from "thick" long after they've split apart.