the.com/law of supply

means The economic principle that, all else being equal, as the price of a good rises, producers are willing to offer more of it for sale — and as price falls, they offer less.

from 'Supply' traces back to Latin 'supplere' — 'to fill up, complete' (sub- 'up from below' + plere 'to fill') — the same root behind 'supplement' and 'complete.' It entered English via French in the sense of furnishing or providing something needed. The economic pairing with 'demand' sharpened in the 18th and 19th centuries as thinkers like Adam Smith and later classical economists formalized how price and quantity-offered move together — turning an old word for 'filling a need' into a cornerstone of market theory.