From my understanding, the caret character (
^) has been used to indicate Ctrl-key combinations since the early UNIX days, if not earlier. Why was this character used to indicate this? Was it simply that the symbol wasn't being used for anything else at the time, or is there an etymological history where that makes sense?
Some things have used alternate notation; for example, Emacs stands out for using
C- instead, and many user manuals simply write
ctrl-, much as how
alt- is still commonplace (a notable exception being Apple's modern use of
⌥ for Option, and similarly
⌘ for Command, which of course used to be represented with the Apple logo instead, with both open and filled variants on the earliest Apple computers).
The dictionary definition of caret doesn't make any nod to this usage, and instead only offers:
a wedge-shaped mark made on written or printed matter to indicate the place where something is to be inserted
and while Wikipedia describes the usage as a control character it states nothing about the history of this usage so far as I can find.