Here is the link to a preview chapter (head and neck - perfect for us ) of the book mentioned above. It is very interesting for us I think for understanding the pain and tension. Maybe the mentioned therapies are also good, but better ask an ES expert doctor before doing.
Surprisingly, there is even ES mentioned there (Page 74).
I think you should also be interested in that, @vdm, as military neck is also described here. I think they are more likely to assume the Eagle Syndrome as the cause. But that’s really an interesting question furtheron.
I’m not 100% sure about its origin but I’m guessing it’s from this book:
Myofascial Pain and Dysfunction: The Trigger Point Manual, Vol. 1 - Upper Half of Body
Authors: David G. Simons; Janet G. Travell; Lois S. Simons
Publisher: Williams & Wilkins
Published: October 1998
Chapter05.pdf (6.2 MB)