Grave expression

[Firiffic]

Where does the phrase "someone just walked over my grave" used when describing a shiver down the back originate from?

[Quizmonster]

The following (modified) sentence appears in 'Macbeth' ..."By the tingling of my thumbs, something wicked this way comes." (It's not 'tingling' in Shakespeare's version, but I'm sure AnswerBank won't allow me to use the actual word. If you need a clue, it's what you feel if you stick a needle into your finger.)
There's also the idea, if you shiver, that that means someone is walking over your eventual grave-site. An itchy palm means money is coming, 'burning' ears mean someone is talking about you and there are many other similar physical beliefs.
All of these examples are superstitious hangovers from the days of witchcraft/angels etc, when people believed they were constantly being offered signs and warnings of distant or future events.