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 bootstra

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).