Today I learned that “vi” got its name from the ex editor. Now ex
was a 1978 UNIX line editor. (Remember ed?) As the wiki article describes:
ex was eventually given a full-screen visual interface (adding to its command line oriented operation), thereby becoming the vi text editor.
So “vi” stands for the visual interface of the ex
editor.
Try ex
on a modern machine and you’ll get vi
in line edit mode: