night eye n [Appar a calque of Chinese 夜眼 (yè yǎn), but the path of transmission is unknown. According to the 16th century Bencao Gangmu (“Compendium of Materia Medica”) of Li Shizhen, the “night eyes” enable the horse to walk at night and are used to treat, among other things, toothache.] formerly Sth, Midl, now more widely known
The callosity or “chestnut” found on the inside of the leg of horses and other equids; occas applied also to the “ergot,” a similar callosity occurring on the underside of the fetlock.
1835 Amer. Jrl. Med. Sci. 16.333 csVA, Observations on the Crusta Genu Equinæ, (Sweat or Knee Scab, Mock or Encircled Hoof, Knees, Hangers, Dew Claws, Night Eyes, or Horse Crust,) in Epilepsy. By John S . Mettauer, M. D. of Prince Edward County, Virginia. . .The substance designated by the several appellations at the head of this article, is furnished by the horse; four oval surfaces, situated on the inner aspects of the extremities, near the knees, are the parts of the animal from which it is obtained. 1859 Ohio Valley Farmer 4.179/3, Others have treated the disease [=colic in horses] successfully by taking off [sic] the horny substance which grows on the inside of the animal’s leg, (called “night-eye,”) about one table-spoonful cut or pounded fine. 1890 Sacramento Daily Rec.–Union (CA) 24 May 3/1 AL [Black], To cure toothache the child who suffers must . . . put into his tooth a bit of the “night eye” of the left hind heel of the meanest mule on the plantation. 1916 Nashville Tennessean & American (TN) 15 July [6]/2, [Advt:] Strayed— . . pacing bay horse, 8 years old; scar on right leg above night eye. 1925 Amer. Folkl. Soc. Memoirs 203 MD, Warts that grow on the horse’s knee and fetlock are called “Night eyes,” because they give horse [sic] the power to see at night; if cut off, the horse will go blind . 1925 Courier–Jrl. (Louisville KY) 9 Aug sec 2 4/3, It may be of interest to note some of the few cardinal points in which the jack, mule and horse differ. . . Second, the absence of chesnuts or night-eyes on the hind leg of the jack yet always found on the hid [sic] leg of the horse. Mules nearly always have them on their hind legs, though some do not have them. 1938 in 1970 Hyatt Hoodoo 1.453 cSC, These horses go up an’ down the street. . . You see them little black places on em? . . Dat’s wha’ choo call horse night-eyes. Ibid 2.1259 swTN, It’s a thing on de laigs, it’s called a night-eye. 1939 San Francisco Examiner (CA) 26 May 17/7, Photographing the chestnut or “night eye” of each thoroughbred . . , Brown asserts will preclude all possibility of ringing. c1943 Hench Coll. cVA, They . . explained that people often jokingly explain the fine vision horses have by saying that there are two oval spots on their legs which are their “night eyes.” All talked as if everybody knew about these eyes. 1947 Miami Daily News (FL) 31 Mar sec B 2/1, Photographing of the “chestnuts” or “night-eyes” on legs to identify thoroughbreds was introduced this winter at Hialeah by Dr. Catlett. . . Also being used in New York, the system is the latest in a series of movies [sic] to guarantee the public that the horse listed on the program is actually the one running. 1958 Browne Pop. Beliefs AL 109, Night eye (a sorelike growth on a mule’s front leg) is good for toothache. [Ibid 229, Horses with night lights on their legs (black wartlike patches) can see in the darkness.] 1991 DARE File seWI, Night eyes are the horny growths on the inside of a horse’s legs. They can be used as a means of identification. 2022 DARE File—Internet [Jockey Club web site], The Jockey Club may ask for a set of night-eye photos to assist in the identification of horses with no white markings or gray/roans.