This is the first I've read of "TUI" standing for what I have to assume is "terminal user interface"? I'd call them CLI (command line interface). When did this TUI acronym start? What does it mean? Everyone else seems to know it and use it without defining.
I dont know when it exactly started but I've heard and use this term at least 15 years. CLI != TUI. TUI is more like a "standard" window (GUI) but all text based.
TUI, Textual User Interface today tend to be a 2D terminal graphic, from ncurses to framebuffer. Classically it's simply a 2D UI based on text, so for instance Plan 9 ACME editor is a TUI since it's graphic but you can write text anywhere creating and changing menus, toolbars etc.
I think there is no official Jargon File entry to clarify this, 99% of the time people name TUI an ncurses UI, witch is a debatable since it can be not really usable as text and so as Terminal User Interface, but a CLI is also a terminal user interface.