> "bang" came from the "bang path" of UUCP email addresses

"Bang" was in common use by computer users around 1970 when I was working at Tymshare. On the SDS/XDS Sigma 7, there was a command you could use from a Teletype to send a message to the system operator on their Teletype in the computer room. I may have this detail wrong, but I seem to recall that it included your username as a prefix, maybe like this:

  GEARY: CAN YOU LOAD TAPE XYZ FOR ME?

What I do remember clearly is that there were also messages originated by the OS itself, and those began with "!!", which we pronounced "bang bang". Because who would ever want to say "exclamation point exclamation point"?

The reason this is vivid in my mind is that I eventually found the low-level system call to let me send "system" messages myself. So I used it to prank the operator once in a while with this message:

  !! UNDETECTABLE ERROR

I was proud of calling it an "undetectable" error. If it was undetectable, how did the OS detect it?