Pretty sure 'TTY' comes from "Teletype".

...is "Bing"! (Discovered in a fortune cookie that came with sushi bought in a cafeteria in a building housing a Microsoft R&D team. When I saw it, I found a Chinese coworker and asked her what was the Chinese word for "disease", and she cheerfully responded "Bing!" -- at which point other coworkers in earshot cracked up and she said something like "Wow, I never thought of that!". This was only a few months after the Bing launch....)