I want to make sure the idiom "off the wall" means.
I learned today about the idiom "off the wall".
I want to know the origin of the idiom.
In this idiom, preposition "off" means to be away from a place or postion
and I guess "off the wall" means literally something is away from a "wall"
and it refers that something is away from usual thing and it is different from other.
Am I correct?
If I am not, could you correct me?
Thank you very much!

Question

I want to make sure the idiom "off the wall" means.
I learned today about the idiom "off the wall".
I want to know the origin of the idiom.
In this idiom, preposition "off" means to be away from a place or postion
and I guess "off the wall" means  literally something is away from a "wall" 
and it refers that something is away from usual thing and it is different from other.
Am I correct?
If I am not, could you correct me?
Thank you very much!

Answer

"Off the wall" is a phrase that people use to express something as crazy, wild, odd, bizarre etc.  
 
Example: That party was off the wall!

Answer

The expression comes from the late 1950s, but the originating metaphor is unknown. It likely refers to a sport like baseball, where a ball may literally be played as it caroms off the wall, often with wild and unpredictable bounces.