When you start the Computer up. What is the first thing the computer does every time you take it for granted
2 word answer

boots up

Fuse
It describes the Boot up sequence also known by a 4 word sentence which has been semi-abbreviated to 2 words

I was thinking of POST as one of the words but "power on self test" is already four words by itself.

Fuse That is the answer but nearly everybody on the Computer forums say "POST test" another way is to say "Post Beep" which reminds you the computers starting (But only the knowledgable know what checks its ran in those brief seconds)

So it is in a way a bit of a catch-question

Just to show you what Hits the "POST beep" name generates alone on Google look at this

And here is a good page about the test itself
www.computerhope.com/beep.htm