The main question is: what are you trying to achieve?
If you are trying to keep AW and UKP out of your search history, then use Incognito or Private mode as people have suggested.
Having a moment and forget to use incognito? Most browsers now offer the option of deleting the last hour of browsing history, which is handy on a shared computer.
Tor, I2P, and VPN are all designed to mask your browsing from your ISP and the government, and most Tor/I2P setups also include a browser that's configured to run in Incognito mode (above). I would suggest that most people don't need this unless they are on a work-based connection or are really paranoid about getting caught. At other people have suggested, Tor and I2P also carry other risks, and I'd argue that that having them installed is bound to raise questions from those who understand IT.
Live/temporary operating systems are handy as a 'leave no trace' option. There are distributions that include above masking (Tor, I2P, etc,) and Incognito browsers, and it's easy to burn onto a CD or keep on a USB memory stick.
One thing that people haven't mentioned. OP, it might be that your device is remembering the word 'adultwork' or 'ukpunting', which would be a keyboard option rather than a browser one. You can delete custom dictionary words in the keyboard settings screen.