Hjelm Dyb and Helm's Deep

Hjelm Island from Hjelm Dyb, photo courtesy of Dr. B. A. Kaiser

                                  

I just learned that there is a small island off the coast of Denmark, called Hjelm, which is separated from the mainland by a body of water called Hjelm Dyb.*

And yes, Tolkien fans, Hjelm Dyb means exactly what you think it means, though obviously this is 'deep' in a different sense which Tolkien knew also quite well ('The love of the Elves for their land and their works is deeper than the deeps of the Sea' [FR 2.vii.365]).

I don't know if Tolkien knew about Hjelm Dyn, but he did have Gimli say of Helm's Deep: "Give me a year and a hundred of my kin and I would make this a place armies would break upon like water" (TT 3.vii.532).

Elsewhere in the chapter Helm's Deep he continues to use sea related comparisons to describe this stronghold:

• "the great stones of it were set with such skill that no foothold could be found at their joints, and at the top they hung over like a sea-delved cliff" (TT 3.vii.533); 
• "But the Hornburg still held fast, like an island in the sea" (TT 3.vii.536).

He also compares the attacking forces to the sea three times.

• "They wavered, broke, and fled back; and then charged again, broke and charged again; and each time, like the incoming sea, they halted at a higher point" (TT 3.vii.533).
• "Against the Deeping Wall the hosts of Isengard roared like a sea" (TT 3.vii.535).
• "Over the wall and under the wall the last assault came sweeping like a dark wave upon a hill of sand." 

So, this is all quite fun and fascinating and it certainly wasn't beyond Tolkien to take a phrase like 'Hjelm Dyb' and transform it. Whether he knew about the Danish island and the body of water is the question. It may well be unanswerable. I'd be interested to know if anybody else has any ideas. Obviously, Danish Tolkien fans would be most likely to see the words 'Helm's Deep' and recognize the echo, whether Tolkien intended it or whether it's coincidental. 

I have learned since first posting this that a Danish historian named Casper Clemmensen has just published a book on Tolkien and Jutland, Tolkien og det mytiske Jylland, which makes this and other similar observations. 

From Google Maps of course

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*I would like to thank my good friend, Dr. Brooks Kaiser of the University of Southern Denmark for letting me know about Hjelm and Hjelm Dyb. May the wind be ever at your back as you sail there.