in the logo discussion the term "Testing out of the box" came up as the thought behind the name. I think this is a great slogan for the project as well, so I am wondered why it is not used more prominently.
When I google for it I come up with http://testoob.sourceforge.net/ which was last updated in 2009 on PyPI and looks pretty dead to me.
On the other hand, tox is often used more like a makefile nowadays (do more stuff additionally to testing like building documentation, deployments whatever should be automated and easy to reach) ... at least by me :) - so as much as I like the slogan it might actually not cover completely what tox is.
I also explain tox as a command line CI frontend sometimes, but that is obviously only making sense to people who know what CI is and what challenges it presents.
I would be interested in your opinion about what tox is and how one could describe it in a few words and if you think that a slogan might be a nice thing to have.