1
general::
Phrase(s): boot up
[of a computer] to begin operating; to start up one’s computer. • He turned on the computer and it booted up. • Try to boot up again and see what happens., Phrase(s): boot something up
to start up a computer. • She booted her computer up and started writing. • Please go boot up your computer so we can get started.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Start a computer, as in When you've booted up, it's best not to turn off the computer until you're done for the day. The term, dating from the late 1970s, was a shortening of bootstrap, another computer idiom referring to using one set of instructions to load another set of instructions. Also see LOG IN.
American Heritage Idioms