taken from here
The term bootstrapping refers to a Dutch legend about a boy who was able to fly by pulling himself up by his bootstraps. In computers, this term refers to any process where a simple system activates a more complicated system.
the command "make bootstrap" is usually issued when one wants to compile GCC
(you need a compiler to compile a compiler)... the concept resembles the dutch legend due to the fact that, basically, first some basic tools are compiled, then a compiler is compiled, then a compiler is compiled with the compiler that was compiled, etc... i hope this helps you understand the idea a little more...