Bootstrap is a word that irks me. A language that can compile itself. Or a startup that is self sufficient? Ok. But then some javascript framework. And a hundred other uses. What's up with that?
The original meaning came from one of the stories of Baron Münchhausen where he supposedly fell into a bog but escaped by pulling himself up by his own bootstraps. So the basic concept of self-sufficiency gives you the meaning of bootstrapping a compiler, or your OS's bootstrap loader, or a bootstrapped startup. Stuff like Twitter Bootstrap does stretch the meaning somewhat (I guess the idea is that's it's an easy way to get started on your website).
Bootstrap has always meant starting a business using your own money/resources. I guess that's why the Twitter guys named their framework it - you can get a website together to a decent standard without needing to pay for a designer (the 'bootstrap framework' helps you bootstrap a business).