Before I go into detail, let’s take a quick look at the original definition of jailbreak.
1. an escape from prison, especially by forcible means.
The “prison” here is Apple’s restrictive “walled garden” operating system (iOS) that allows little to no customization by its users. “Forcible means” is the software that allows users to hack into Apple’s delicately crafted OS. And the “escape” is users having fun in this new freer playground. You get the picture.