Today in Britain today is Boxing Day, when traditionally tradesmen are given a present of money. This present is called a Christmas Box, but during the rest of the year, of course, it's called a tip, which makes a nice easy thing to spot after the rigours of Christmas.
To make things even easier, tip is really four words. There's the sort of tip that's the far end of something, like a finger, or a mountain, or a knitting needle; there's the tip that's a payment given for services rendered (in Britain it's usually 10%, and only given if you get good service); there's the light/glancing blow tip, such as one might make when playing cricket; and (also in Britain) there's a rubbish dump tip where refuse has been, well, tipped.
This last meaning is widely and commonly transferred: a student's untidy room is a tip.
This is vastly satisfying to point out, and I recommend it to friends throughout the world.
Spot the Frippet: tip. The end-of-something word comes from the Old Norse typpa; the dumping word is rather mysterious, but is related to topple, which comes from the Old Norse toppr, tuft; the hitting word is also mysterious, but might comes from the Low German tippen; and the payment-for-services word is probably related to tippen, too.