"Typewriter" was what early Unix systems called a terminal. This usage goes all the way back to the First Edition of the Unix Programmer's Manual, dated November 3, 1971. For example, the description of the "hup" command was "hup hangs up the phone on the typewriter which uses it." The abbreviation TTY, which occurs widely even in modern UNIX systems, stood for "Teletype." The generic term "typewriter" was probably used because "Teletype" was a registered trademark of AT&T subsidiary Teletype Corporation and was too specific. The name "Teletype" was derived from the more general term, "teletypewriter"; using "typewriter" was a different contraction of the same original term.