Sound which accompanies the illicit snatching of a small item, used to great effect in The Simpsons. Two of my favourite examples:

• Snake snatching the handbag of Chief Wiggum, who is undercover disguised as a woman: "Somebody stop that awful, awful man!"
• Jasper Johns stealing a painting from Marge, who has been painting on the roof of her house after Homer flooded the whole of Springfield as an artistic statement. Johns then speeds off in his stolen speedboat.

What did people say when snatching something before the word yoink was invented? "Ah ha - I have taken it from you!"? No, that just doesn't work. Since the time when one caveman first stole a leg of mammoth from another caveman, there has been a yawning gap in our language - an exclamation to be used when lightheartedly taking something from under the nose of its legitimate owner.

The key to the proper use of yoink is a lighthearted or impish attitude on the part of the thief in the quick removal of a physical object- George W. Bush, for example, could not have said "Yoink!" upon is inauguration, whereas Robin Hood would have said it regularly.