1580s (n.), 1670s (adj.), probably dim. of doue "poorly dressed woman" (early 14c.), of uncertain origin. The modern use of dowd (n.) is most likely a back-formation from dowdy. "If plaine or homely, wee saie she is a doudie or a slut" [1581].
"You don't have to be dowdy to be a Christian." [Tammy Faye Bakker, "Newsweek," June 8, 1987]