ar·row·root 
(ărō-rt′, -rt′)
(ărō-rt′, -rt′)n.
1.
a. A starch obtained from the rhizomes of a tropical American perennial herb (Maranta arundinacea). It is used especially in cooking as a thickener.
b. The rhizome of this plant, cooked and eaten as a vegetable or used for starch extraction.
c. The plant itself.
2.
a. The edible starch obtained from the rhizomes or tubers of various other plants, including coontie.
b. Any of these plants.
[By folk etymology from Arawak aru-aru, meal of meals (from its being used to draw poison from arrow wounds).]
Word History: The arrowroot is just one of many plants that the European settlers and explorers discovered in the New World. The Arawak, a people who formerly lived on the Caribbean islands and continue to inhabit certain regions of Guiana, named this plant aru-aru, meaning "meal of meals," so called because they thought very highly of the starchy, nutritious meal made from the arrowroot. The plant also had medicinal value because its tubers could be used to draw poison from wounds inflicted by poison arrows. The medicinal application of the roots provided the impetus for English speakers to remake aru-aru into arrowroot, first recorded in English in 1696. Folk etymology—the process by which an unfamiliar element in a word is changed to resemble a more familiar word, often one that is semantically associated with the word being refashioned—has triumphed once again, giving us arrowroot instead of the direct borrowing of aru-aru.