Who thought of the term HC? When?

Somebody asked me who actually thought of HCM and when. What I do know is that in 1979, Theodore Schultz and Sir Arthur Lewis received the Nobel Price in Economics for their pioneering work in human capital.
At Reuters.com I read that the term "HC" was coined in 1961 by economist Theodore Schultz. Typically, the term is used to describe the value of the investment in training, education, health care and the like that organizations (or countries/regions) are making.
Was Schultz actually the first who used the term? Or does HCM have even older roots?