[Falkon1313]

It's been in use since at least the late 1980s to early 1990s. I believe it was in the Turbo Pascal for DOS documentation I used back then, as well as Turbo Vision and some other things. I also worked on a TUI library for Euphoria in DOS around that time.

And it means a full-screen Text User Interface, which is quite different from a line-oriented CLI (Command Line Interface). Instead of a command line, you have a full screen interface with menus, dialogs, buttons, checkboxes and radios, listboxes, windows, scrollbars, etc. Just all in text mode using things like the box drawing and shading characters.

So at least 30 years ago. Probably the early 80s, although I'm not sure of that. But that's when some programs started going from CLI or forms-based to actually using that full-screen TUI style.

The earlier forms-based programs were basically just a hard-coded text-mode screen with blank fields that you could fill in the blanks, then hit a key to either submit, escape back out, or use a hotkey to pull up a different form screen. They didn't have the various interface widgets that we got used to with the TUIs and later GUIs.