U.S. [A use of Sp. loco insane, mad.] One of several leguminous plants (chiefly species of Astragalus) found in the western and south-western U.S., which, when eaten by cattle, produce loco-disease. More fully loco-plant, loco-weed.
1883. W. H. Bishop, in Harper’s Mag., March, 503/1. The loco, or rattle-weed, met with also in California, drives them [horses] raving crazy.
1886. Cornh. Mag., Sept., 297. A weed called ‘loco’ has of late years largely increased in some of the cattle-ranges of Texas and the Indian territory, owing probably to an increase in the rainfall.
1889. Science, XIII. 176/1. A curious affection which exists among horses in north-western Texas, known as ‘grass-staggers,’ which is caused by eating the ‘loco-weed,’ which gives rise to the saying that the horses are locoed.
b. = loco-disease (Cent. Dict.).
c. attrib. and Comb., as loco-eater, -intoxication; loco-disease, a disease in horses, affecting the brain, caused by eating loco-weed.
1894. Pall Mall Gaz., 23 June, 5/1. A healthy horse refuses loco; but if he once by accident acquires the taste, it grows upon him … and at last he dies of loco-intoxication.
1886. Cornh. Mag., Sept., 297. The animal is doomed, for he has become a confirmed ‘loco-eater.’
1889. Syd. Soc. Lex., Loco-disease.
