#network-science/history
Network diagram
Probably the first network diagram was presented in a work by Jacob Moreno for group therapy.
The central idea of group therapy (or group psychotherapy) is to treat a social group as a group and treat individuals in the context of a group setting, not a collection of individuals. Moreno believed that, in order to realize effective intervention for group therapy, one must have good assessment tools for the group, and he invented sociogram.
Random networks
Moreno and Jenning invented random graphs as a way to assess the significance of the network structure.
...in which they consider a random graph, where a node has the same number of directed edges emanating from them that are connected to other nodes uniformly at random. Their papers used the random model to define the structure, where an edge represents the tendency of social ties to be reciprocated.
Reference
The Early Beginnings of Social Network Analysis and the Potential Use for Homeland Security | by Angi English | Homeland Security | Medium
Firsts in network science – Petter Holme
Models and Methods in Social Network Analysis - Google Books