More for my own reference. Link: Wikipedia
The first known use of the concept was by L. J. Hanifan, state supervisor of rural schools in West Virginia. Writing in 1916 to urge the importance of community involvement for successful schools, Hanifan invoked the idea of “social capital” to explain why. For Hanifan, social capital referred to:
those tangible substances [that] count for most in the daily lives of people: namely good will, fellowship, sympathy, and social intercourse among the individuals and families who make up a social unit..