The idea of the API is much older than the term itself.

British computer scientists Maurice Wilkes and David Wheeler worked on a modular software library in the 1940s for EDSAC, an early computer.

The subroutines in this library were stored on punched paper tape organized in a filing cabinet.

This cabinet also contained what Wilkes and Wheeler called a "library catalog" of notes about each subroutine and how to incorporate it into a program.