means A complex carbohydrate that plants store as energy — found in foods like potatoes, rice, and wheat — and which, when extracted, stiffens fabric into crisp collars and cuffs.

from From Old English 'stercan,' meaning to stiffen, and a close cousin of 'stark,' which once meant rigid or hard. The thread connecting them runs through a Germanic root for stiffness — the same family that gives German 'Stärke' (both 'strength' and 'starch'). So the laundry sense and the food sense met later: the stiffening agent was named for what it does to cloth, and the plant substance that made shirts crisp lent its name to the molecule chemists eventually found everywhere.