Yum was borrowed from yellow dog Linux.

To be pedantic, yum was not from Yellow Dog, it is Yellow dog Updater Modified after all. It was a rewrite of the Yellow Dog Updater by people at Duke University. (Yellow Dog Linux was based on Red Hat.)

There was a lot of competition around package managers back then. For RPM, there were also urpmi, apt-rpm, etc.

Which in turn was based on RHEL/CentOS: https://en.wikipedia.org/wiki/Yellow_Dog_Linux