late 14c., dauben, "to smear with soft, adhesive matter, to plaster or whitewash a wall" (Dauber as a surname is recorded from mid-13c.), from Old French dauber "to whitewash, plaster" (13c.), perhaps from Latin dealbare, from de-, here probably meaning "thoroughly," + albare "to whiten," from albus "white" (see alb).
From 1590s as "to dress or adorn (a person) without style or taste." Painting sense is from 1620s. Related: Daubed; daubing, daubery. As a noun from mid-15c. as "daubing material, cheap kind of mortar;" 1761 as "inartistic painting."