Totally agree with your comment. Just came in to leave for others: I believe "TTY" stands for "Teletype"(writer). Learned fun facts I didn't know when I hit google to double check: the original teletypes are descendants of a morse-code printing device called the "teleprinter" (from the 1830s!") One of the early popular devices for encoding and printing typographic characters was patented by Emile Baudot(for whom "Baud rate" is named) in 1879! This means that the commercial mechanical typewriter barely predates the teletype.