Definition
Mottle is a disease symptom comprising light and dark areas in an irregular pattern, usually caused by a virus; often used interchangeably with mosaic.
Etymology. 1676, probably a back-formation from motley. motley: c.1386, from Anglo-Fr. motteley, probably from O.E. mot "speck" (see mote). "Diversified in color," especially of a fool's dress. Hence, allusively, "a fool" (1600).