1660s, "painting or drawing done in different tints of a single color," from Latinized form of Greek monokhrōmos, also monokhrōmatos, "of a single color," from monos "single, alone" (from PIE root *men- (4) "small, isolated") + khrōma (genitive khrōmatos) "color, complexion, skin" (see chroma). As an adjective from 1849. Photographic sense is recorded from 1940.
Proto-Indo-European root meaning "small, isolated."
It forms all or part of: malmsey; manometer; monad; monarchy; monastery; monism; monist; monk; mono; mono-; monoceros; monochrome; monocle; monocular; monogamy; monogram; monolith; monologue; monomania; Monophysite; monopoly; monosyllable; monotony.
It is the hypothetical source of/evidence for its existence is provided by: Greek monos "single, alone," manos "rare, sparse;" Armenian manr "thin, slender, small."