Nekem a fb-tól rémlik elsőként a kifejezés ilyen irányú használata, ott van egy magyarázat is hozzá:
The Graph API is named after the idea of a "social graph" — a representation of the information on Facebook. It's composed of nodes, edges, and fields. Typically you use nodes to get data about a specific object, use edges to get collections of objects on a single object, and use fields to get data about a single object or each object in a collection. Throughout our documentation, we may refer to both a node and edge as an "endpoint". For example, "send a
GETrequest to the User endpoint".
https://developers.facebook.com/docs/graph-api/overview
Persze ettől még simán lehet, hogy oda is máshonnan érkezett..