To juice the root: Even though it was very humid and they were on a 10-day canoing trip, Jane milked John's root like she was back in grade school and made him very happy.
It's an old expression actually originating from a peg, with the Rooter being the snout, and the Tooter being the tail. So basically it means the whole hog from snout to tail. But has come to mean from head to toe.
In a general sense,it means to go from front to back. It originated in the south when southern blacks were speaking about pigs and hogs. The roota (rooter) is the nose of the pig. A pig uses it's nose to root up dirt. The word toota (tooter) has always been a term for booty. The nose of the pig is in the front,and the booty is in the back. Front to back.