I am sure someone can craft a better answer however to me bootstrapping is related to the boot process where the process that starts up on the cpu initially must start the rest of the OS.
https://stackoverflow.com/questions/1254542/what-is-bootstrapping
Provisioning implies assignment and potential utilization of resources. For instance, You provision VM's from the hardware resources available on the system or group of systems. You even hear the term over-provision in this context meaning you have allocated more potential resources than are currently available knowing that many of the provisions are under-utilized.
You can also provision files, settings, etc. in existing systems with a configuration management system such as puppet or chef.
I hope that helps. If something is unclear I would be happy to try for a better explanation of anything specific.