Perhaps it's a reference to how Emacs does "everything" and some has also joked that Emacs is an OS with a text editor

Back then Emacs was considered what we call in modern software 'bloatware': resource hungry, big and full of feature creep.

BTW, in early versions of Slackware emacs was bundled in its own software category due to its huge size when selecting which packages to install on first boot.