double up
phrasal verbdouble up (on something/with somebody) 
- (informal) to form a pair in order to do something or to share something
- We'll have to double up on books; there aren't enough to go around.
 - They only have one room left: you'll have to double up with Peter.
 
 
double up/over | double somebody up/over 
- to bend or to make your body bend over quickly, for example because you are in pain
- Jo doubled up with laughter.
 - I was doubled over with pain.