Boot

1. boot, alternatively referred to as boot-up or sometimes start-up, booting is the process of powering on a computer and getting into the operating system.
2. boot-strap is the process of build something up in stages until it is refined or complete.

This is just what the boot process does in a computer. It starts with a simple boot program and through stages arrives at executing the full operating system (OS).

I suspect that boot is short for bootstrap.