diddle

From dialectal duddle (“to trick”) (16th century), and diddle, duddle (“to totter”) (17th century), perhaps dissimilated from dialectal didder, dither (“to shake, tremble”), from Middle English dideren (“to shake, quiver, tremble”) and Middle English bididren (“to seduce, deceive”), from Old English bedidrian, bedyderian (“to trick, deceive”). Compare also Saterland Frisian diedelje (“to play or sing without a melody”), Dutch bedodden, bedotten (“to trick, fool, diddle”), German Low German Diedeldentjes (“pranks, pranking”). Possibly influenced or reinforced by the name (which itself was probably chosen as an allusion to duddle) of the swindling character Jeremy Diddler in Kenney's Raising the Wind (1803).

Meanings "to have sex with" and "to molest" are from the 19th century; "to masturbate" is from the 1950s. Compare dildo.