Arrowroot

Origin

arrow + root, from being used on wounds from poison darts to absorb the poison.http://www.etymonline.com/index.php?term=arrowroot

Full definition of arrowroot

Noun

1. A large perennial herb ( - family ) native to the Caribbean area. It has large green leaves about 15 centimeters long with white stripes.
2. (uncountable) A starchy substance obtained from the roots of the arrowroot plant used as a thickener.