unaccustom

From un- +‎ accustom.

unaccustom (third-person singular simple present unaccustoms, present participle unaccustoming, simple past and past participle unaccustomed)

1. To make or become used to a change from something one was accustomed to.
   • 1888, W.H. Michael, Message from the President of the United States to the Two Houses of Congress at the Commencement of the First Session of the Fiftieth Congress with the Reports of the Heads of Departments and Selections from Accompanying Documents:

     Is is the part of statesmanship to give up a revenue so easily collected, to unaccustom our people to its payment and to do away with all machinery for its collection, when, unless we are more favored than the other nations of the world, there will come a day when it will all be needed?

   • 1897, Navy and Army Illustrated - Volume 5, page 238:

     On a man-of-war putting to sea, the ship's company have to unaccustom themselves to living on the fat of the land -- said "fat" consisting of one pound of fresh beef (including lean and bone), and one and a-half pounds of vegetables for each man per diem-- and instead of eating baker's bread ("soft tack") they crack and crunch ship's biscuit ("hard tack").

   • 1934, Stevens Indicator - Volume 51, page 123:

     The hardest thing for me to unaccustom myself to will be commuting.