whitewash (v.) Look up whitewash at Dictionary.com
1590s, "to wash a building surface with white liquid," from white (adj.) + wash (v.). Figurative sense of "to cover up, conceal, give a false appearance of cleanness to" is attested from 1762. Related: Whitewashed; whitewashing. The noun is recorded from 1690s; in the figurative sense from 1851. The earlier verb was whitelime (c.1300).