SHUT UP & SHUT DOWN

My 9 year old son one day asked me "Mom, what's the difference between SHUT UP and SHUT DOWN?

I explained to him that SHUT UP means that you need to stop talking. SHUT DOWN means closing down some office or even computer.

He said "But SHUT UP and SHUT DOWN are supposed to be Antonyms... Having opposite meaning. Why are they not that way?"

:-):-) :-) What to say? 😂😂