loco-weed (n.)

"mad, crazy," 1844, American English, from Spanish loco (adj.) "insane," of uncertain origin, perhaps from Arabic lauqa, fem. of 'alwaq "fool, crazy person." Loco-weed was the name given to species of western U.S. plants that cause cattle and horse diseases that make them stagger and act strangely. But the adjective seems to be the older word.

"plant not valued for use or beauty," Old English weod, uueod "grass, herb, weed," from Proto-Germanic *weud- (source also of Old Saxon wiod, East Frisian wiud), of unknown origin. Also applied to trees that grow abundantly. Meaning "tobacco" is from c. 1600; that of "marijuana" is from 1920s. The chemical weed-killer is attested by 1885.

1540s in botany, a large genus of plants that include the milkvetch, loco-weed and goat's thorn; 1560s in anatomy in reference to a type of bone, usually in or near the ankle. Historically these bones, especially those taken from deer, were used as a type of die for games and fortune telling. It is attested from 1560s in architecture as a type of molding. All senses are from Greek astragalos "neck vertebra; ankle bone; knuckle-bones (used as dice)," which generally is considered to be from the same root as osteon "a bone" (see osteo-), but Beekes says they are unrelated.