A brief history of interfaces

As mentioned in the Preface, the use of programming interfaces as the means for one application (or application module) to interact with another is by no means new. In fact, the first use of the term API can be traced back to the 1968 publication Data Structures and Techniques for Remote Computer Graphics by I. W. Cotton and F. S. Greatorex, Jr. The paper described an approach to achieving hardware abstraction, modularity, and reusability by implementing hardware-agnostic APIs that can be remotely accessed from multiple display devices.

For more information on this publication, please refer to the following link:
https://www.computer.org/csdl/proceedings/afips/1968/5072/00/50720533-abs.html

However, in spite of the obvious similarities with the contemporary use of interfaces, it is difficult to tell whether such early use of the term had any influence...