Back Out Meaning

(idiomatic, computing) To undo a change.

Example: To reverse a vehicle from a confined space.
  He backed out of the garage.
  She backed out of organizing the fund-raising.
1920, Herman Cyril McNeile, Bulldog Drummond Chapter 1
  The girl threw back her head and laughed merrily. "You poor young man," she cried; "put that way it does sound alarming." Then she grew serious again. "There's plenty of time for you to back out now if you like. Just call the waiter, and ask for my bill. We'll say good-bye, and the incident will finish."
1921, Nephi Anderson, Dorian Chapter 1
  "I can back you out."
  "How? Doin' what?" they asked.
  "Crossing the canal on the pole."
  "Shucks, you can't back me out," declared one of the boys, at which he darted across the swaying pole, and with a jump, landed safely across. Another boy went at it gingerly, and with the antics of a tight-rope walker, he managed to get to the other side. . . .
  "All right, Carlia," shouted the boys on the other bank. . . .
  Carlia placed her foot on the pole as if testing it. The other girls protested. She would fall in and drown.
  "You dared us; now who's the coward," cried the boys.
1921, Henry Luttrell, Crockford's : Or Life in the West Sketch No. III
  Whatever you throw is your chance. I called five for the main, which is the out chance, and threw seven to it, which is the in chance. If I throw five first, I lose, and if seven I win. You can back me in by betting the odds, or you can back me out, by taking the odds, the bank answers either way.
  I had to back out the changes made to the computer when it became apparent that they had stopped it working properly.