GUEST,Barry Finn: "Nope, dousing the sail(s) would mean to drop it quickly...."

^^^Almost involuntarily, eg: a squall or to surrender. To strike one's sails or colours.

Oddly enough, same as strike oil… or water. As in: “dowsing” or “doodlebuggin'.” Seems to be Grandpa Conchy's 'hokum' month on Mudcat(?)

Middle Low German schlag-ruthe (striking rod) to 16th century Cornish duschen, duschan, (Middle English, to strike or fall.)

“In 1691 the philosopher John Locke, who was born in the West Country, used the term deusing-rod for the old Latin name virgula divina.” [dowsing wiki]