If you drink too much, you get a hangover.
     How do you get rid of it ?

     get rid of is often represented by "off"

e.g. How do you get rid of a hangover ?
     You can sleep it off.

     How else can you get rid of it ?
     I can go running, so I run it off

ii) When you buy something in the sales, you get a certain percentage
off (a reduction) the normal price.

"How much did you get off (the shoes you bought in the sale) ? "
"I got 40% off. "

iii) OFF is also used to show a departure :
e.g. "What time are you off this evening ?"
     "I'm off to Paris tomorrow morning."
     "We're off to the shops now."