mottle n.

late 14c., "parti-colored, variegated in color" (originally of fabric), from Anglo-French motteley, a word of unknown origin, perhaps [OED] based on Old English mot "speck" or a cognate Germanic word (see mote). But Klein's sources say probably from Gaulish. Century Dictionary rejects both. "Diversified in color," especially of a fool's dress. Hence, allusively, "a fool" (1600). As a noun meaning "cloth of contrasting mixed color" from late 14c.

"dappled, marked with spots or patches of color of unequal intensity passing insensibly into one another," 1670s, past-participle adjective from see mottle (v.).