While I'm Emacsposting, my favourite trivia, which unfortunately is no longer true for a couple of versions:

Because starting Emacs from scratch took quite a long time, thanks to copious amounts of elisp that needed to be executed every time, they implemented a clever shortcut to avoid this long startup: Start up emacs at the end of the build process and then have it dump core, then load this coredump when the user executes Emacs.

In case someone doesn't know what a coredump (aka memory or crash dump) is, it is a snapshot image of a process's memory, written to a file. Most commonly taken when the program crashes, so as to facilitate debugging the cause of the crash. Re-loading the core dump basically allowed Emacs to start right back where it had deliberately crashed, thus skipping a bunch of its slow initialization.

Every time I sit there waiting for Civilization to load I wonder why games and other slow-to-start programs don't do this, but by all accounts this was quite hacky and considered an abuse of the coredump feature.