Merriam-Webster's Collegiate® Dictionary, 11th Edition
MOTTLE
I. noun
Etymology: probably back-formation from motley
Date: 1676
a colored spot,
2. a surface having colored spots or blotches, the arrangement of such spots or blotches on a surface, mosaic 5, mottled adjective
II. transitive verb (mottled; mottling)
Date: 1676
to mark with spots or blotches of different color or shades of color as if stained, mottler noun