Depiction of social (network) structure. Jacob Moreno is recognized as the first person to implement the idea.
Apparently, Ella Fitzgerald was likely a node in the very first Sociogram that Jacob Moreno published in 19331. She was at the school from April of 1933 until either the end of 1933 or early 1934. It is not totally clear whether she was in the sociogram or not. I could not find “EF” in the node names (assuming that the node names are initials).