As someone who came up using Borland's Turbo Pascal, Turbo C, and Turbo Vision (their OOP UI framework), it was called CUI (character-based user interface) to distinguish from GUI, which became relevant as Windows became dominant.

I never heard "TUI" until the last few years, but it may be due to my background being Microsoft-oriented.

One of the only references I can find is the PC Magazine encyclopedia: https://www.pcmag.com/encyclopedia/term/cui