People (mistakenly, I believe) thought that "master branch" was derived from the disk and database "master"/"slave" metaphor, which had started being eliminated

People (mistakenly, I believe) thought that "master branch" was derived from the disk and database "master"/"slave" metaphor, which had started being eliminated years earlier. "Master branch" was also a fairly recent coinage (within my career) limited to a few specific tools, so changing it wasn't moving mountains.