"single eyeglass," 1886, from French monocle, noun use of adjective monocle "one-eyed, blind in one eye" (13c.), from Late Latin monoculus "one-eyed," from Greek monos "single, alone" (from PIE root *men- (4) "small, isolated") + Latin oculus "eye" (from PIE root *okw- "to see"). Earlier as a name of a kind of bandage for one eye, also from French.
That this, a hybrid, a Gallicism, and a word with no obvious meaning to the Englishman who hears it for the first time, should have ousted the entirely satisfactory eyeglass is a melancholy illustration of the popular taste in language. [Fowler]
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."
Proto-Indo-European root meaning "to see."
It forms all or part of: amblyopia; antique; antler; atrocity; autopsy; binocle; binocular; biopsy; catoptric; Cyclops; daisy; enoptomancy; eye; eyelet; ferocity; hyperopia; inoculate; inveigle; monocle; monocular; myopia; necropsy; ocular; oculist; oculus; oeillade; ogle; ophthalmo-; optic; optician; optics; optometry; panoptic; panopticon; Peloponnesus; pinochle; presbyopia; prosopopeia; stereoptican; synopsis; triceratops; ullage; wall-eyed; window.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit akshi "the eye; the number two," Greek osse "(two) eyes," opsis "a sight;" Old Church Slavonic oko, Lithuanian akis, Latin oculus, Greek okkos, Tocharian ak, ek, Armenian akn "eye."