Looking at The American College of Rheumatology 1990 criteria for the classification of fibromyalgia (Wolfe, et al. 1990), they indicate that this was first indentified in the late 1970s.
The seminal 1977 paper by Smythe and Moldofsky, “Two contributions to understanding of the ‘fibrositis’ syndrome”, revived interest in the long known but generally neglected syndrome of fibromyalgia (fibrositis). By proposing diagnostic criteria, the authors stimulated other investigators and began a cascade of interest that would lead to the publication of more than 60 research papers and to increasing clinical acceptance of the syndrome.
they also point out that according to some investigators:
fibromyalgia may be thought of as a psychological disorder or, perhaps, a local myofaseial pain syndrome
Wolfe et al. (1990) proposed a set of criteria for diagnosing fibromyalgia which was widespread pain in combination with tenderness at 11 or more of 18 specific tender point sites.
Websites I have visited state that the cause(s) of fibromyalgia are unknown, but seeing as it was starting to be accepted as a real problem in 1977, this has had 42 years for study.
If there is no known cause, I am wondering what the latest consensus is regarding possible causes.
Wolfe, F., Smythe, H. A., Yunus, M. B., Bennett, R. M., Bombardier, C., Goldenberg, D. L., ... & Fam, A. G. (1990). The American College of Rheumatology 1990 criteria for the classification of fibromyalgia. Arthritis & Rheumatism: Official Journal of the American College of Rheumatology, 33(2), 160-172. doi: 10.1002/art.1780330203