Definition of whitewash:
"1952: For walls plaster gave a smooth white surface; or if it was not sufficiently white, or had become discoloured, it could be brightened up with a coat of whitewash or paint. — L.F. Salzman, Building in England, p. 157."
to paint over with a lime and water mixture so as to brighten up a wall or fence; to cover over errors or bad actions
"the houses looked very bright when they whitewashed the whole neighborhood."