Why is an alarm clock going “off” when it actually turns on?

Not true.  In order for an alarm clock to work, the clock doesn't turn on because it must already be on and have been on continuously.

Another oddity of the English language.

First you cut a tree down.

Then you cut the tree up.

For the same reason you don't TAKE a crap, you leave one.

same reason you drive on a parkway and park in a driveway

The same reason you go to the bathroom, to go to the bathroom.  and that most bathrooms don't actually have baths in them?

if it wasnt turned on the alarm wouldnt even work