An error message, still found in Windows 10, is a mistake from 1974
Back in the good old days of the early(er) internet, back when you could do a port search on 21 to find random machines with anonymous FTP access, a lot of the machines you'd find were inevitably Windows machines.<p>A 'trick' used by the file-sharing community in order to hide their files on these anonymous FTP servers was to create some nested directories with these kind of keywords. The FTP server allowed you to create the directories as well as access them (if you knew the full path) but on Windows they would just cause errors or crashes if someone tried to access them. Combine that with the ability of creating directories with just spaces as names and you could hide quite a bit of stuff from the unsuspecting FTP server administrator.