Boot devicecomputer work. It is named after a boot which fits on the foot. The word bootstrap is also closely related, and means, to use something simpler to get something more complex to make itself work better.
Devices that can boot a computer are usually boot disks or boot drives. But network computers use boot chips that get the operating system over the net. Web phones also use such chips to identify the user to the cell network. Boot card standards may let many users boot kiosk computers with full privacy and access to all applications they own.