Using the Google My Search History feature? Make sure you're logged in, then visit Google Blogoscope's Planting My Search History Entries page. Now go look at your search history. You will likely see a link saying:
Click on it, and it takes you to the "search" you never did for those words on Google.
What happened? The comments to Google Blogoscoped's post explain how clever Philip Lenssen put this in a hidden iframe on that page:
border="0" style="width: 0; height: 0; border: 0; overflow: hidden">
That means by visiting the page, you also generated a query sent to Google. And if you are reading this article, the same thing was done to also put this in your history:
Now to see if Google has a way to block such spamming of search history. Hopefully it will.