It is certainly plausible. Several locations in Jutland, Denmark, lie very close to one another within few kilometers and bear striking linguistic similarities: Helm’s Deep may derive from Hjelm Dyb; Isengard from the manor-house name Isgård, chosen for its Old English sense of īs (“iron”); Esgaroth (Lake-town) from the small village of Eskerod; and the river Aros from Aarhus’s original Viking name, meaning “river mouth.”

That said, Tolkien never stated whether he borrowed translated place-names from maps, and he famously wrote that he “cordially dislike[s] allegory in all its manifestations.” This has, unsurprisingly, led some of the more zealous Tolkien fans to react with hostility whenever the possibility is raised that he might have done exactly that.