Once upon a time, Valeri Galtsev galtsev@kicp.uchicago.edu said:
We are talking here CentOS and RHEL Linux. yum is an abbreviation of: "Yellowdog Update Manager". It was originally created by YellowDog Linux project for their Linux distribution.
Actually, yum is Yellowdog Updater, Modified. Seth Vidal (RIP) and others at Duke rewrote YUP (the Yellowdog UPdater) to handle Red Hat Linux.