The Jargon File is still a great resource for this kind of search and if you like these background stories like me you might also enjoy reading all of it.
> [Unix: from `runcom files' on the CTSS system 1962-63, via the startup script /etc/rc] Script file containing startup instructions for an application program (or an entire operating system), usually a text file containing commands of the sort that might have been invoked manually once the system was running but are to be executed automatically each time the system starts up. See also dot file, profile (sense 1).
> [Unix: from `runcom files' on the CTSS system 1962-63, via the startup script /etc/rc] Script file containing startup instructions for an application program (or an entire operating system), usually a text file containing commands of the sort that might have been invoked manually once the system was running but are to be executed automatically each time the system starts up. See also dot file, profile (sense 1).
0. https://www.eps.mcgill.ca/jargon/jargon.html#rc%20file