The only thing even remotely related to graphics I found was references to "TrAA" in forum posts from 2006 (yeah) where I believe they referred to NVIDIA "Transparency AA" or something like that. "TRAA", "TRAA meaning", "TRAA graphics", "TRAA 3D" all gave fully irrelevant results :D

If you make the assumption that "AA" is some form of antialiasing, it's not too bad: first scholar[1] hit expands the acronym to Temporal Reprojection Anti-Aliasing

    [1]: https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=traa+anti+aliasing&btnG=

Yeah, should've tried with "antialiasing". Still, astonishingly obscure given that it's not even a new thing anymore and apparently implemented in UE4 and others.