Fecula

Starch extracted from tubers and roots, such as potatoes, arrowroot, tapioca, etc.
Food thickeners frequently are based on either polysaccharides (starches, vegetable gums, and pectin), or proteins. A flavourless powdered starch used for this purpose is a fecula (from the Latin faecula, diminutive of faex meaning "dregs"). This category includes arrowroot, cornstarch, katakuri starch, potato starch, sago, and tapioca. Liable to deterioration by humidity and odours which are readily absorbed.