tty = T = tube time

tube

1. n. A CRT terminal. Never used in the mainstream sense of TV; real hackers don't watch TV, except for Loony Toons, Rocky & Bullwinkle, Trek Classic, the Simpsons, and the occasional cheesy old swashbuckler movie. 2. [IBM] To send a copy of something to someone else's terminal. "Tube me that note?"

--Jargon File, autonoded by rescdsk.