A small river near Dallas (Texas). John Carmack from id Software, (based at that time in Mesquite, near Dallas) named a new 3D engine after it, following the tradition of others companies whose businesses have to do with computers: Intel did that with the Mercedes and Katmai processors, too.

The river Trinity is still there. Trinity as a ground breaking new engine died to give pass to the Quake 2 engine. Some of the features that originally had to go with Trinity are now found in Quake Arena 3.