Forever, there was a file included in stock Emacs, `spook.el`, which could be hooked up to automatically add random strings of "interesting" keywords to each of your email or Usenet messages (in signatures, or in headers like `X-Spook`).

https://www.gnu.org/software/emacs/manual/html_node/emacs/Ma...

Looks like copyright date of 1988:

https://github.com/emacs-mirror/emacs/blob/master/lisp/play/...

https://github.com/emacs-mirror/emacs/blob/master/etc/spook....

Try `M-x spook RET` in an Emacs buffer.