Why "go off", as in "alarm went off"?

Question

I was wondering why does something _goes off_, when it in fact does the opposite - _bomb goes off_ - it blows up - _alarm goes off_ - it turns on Why not _goes on_?

Answer 1

To "go off" is to occur with little to no control. For example, when a bomb "goes off," it explodes suddenly. Perhaps someone stepped on something or there was a timer, but it seems random or spontaneous to those affected by it. When an alarm "goes off," it begins ringing suddenly. Yes, those are usually planned and set (though not always), but they still seem sudden and sometimes unexpected. Another example of something "going off" is when someone is angry or frustrated. If Person A is upset with Person B, Person A might "go off" on Person B. Person A might yell or shout, might criticize, might insult, etc. with little control/forethought of the words coming out of his/her mouth. You can also "go off the edge" which is to lose control of yourself, to go crazy/insane, or to do something/become someone completely out of character.

To "go on" is to perform with intent. For example, you can go on a trip or an adventure. You can go on the road. These are all intentional.