Using ~ as a shortcut for home directory...

I just stumbled on the question why tilde (~) is used as a shortcut for home directory on Unix. It's very interesting since it never occurred to me to ask this question? :)

Then, there are lot more questions like that one on StackExchange, here is a selection of some interesting ones (to me at least):

• Why is . and .. used for current and parent directories. The answer isn't so clear as for tilde, but it turned out that hidden files (those whose name begins with a dot) are actually consequence of a bug in early versions of ls command (source and Wikipedia page).
• What does /etc mean?
• What was the shell used before Bourne shell?
• Why is dash (-) used to denote options?
• Why isn't umount spelled unmount?
• What is the origin of 'root' account? But note that this question isn't definitely resolved.
• What is the origin of wheel group name?

And, for the end, here is why vi uses hjkl for cursor movement.