Originally Posted by filtherton

It is a metaphor for self reliance based on a physically impossible phenomena. Don't believe me? Try and pick yourself completely up off the ground by pulling up on your shoes.

A more accurate metaphor would also include some sort of support structure, for instance "pull yourself up onto a chair" or "fully utilize the opportunities given to you." Though that second one might be a bit controversial amongst bootstrap proponents since it implicitly recognizes the role other folks play in an individual's success.