the.com/elasticity of demand

means A measure of how much the quantity people buy changes when the price changes — some goods people keep buying no matter what, others they drop the instant the price ticks up.

from Elastic entered English from Latin 'elasticus' via French, tracing back to Greek 'elaunein' meaning to drive or push — originally used for springy, stretchable materials. Economists borrowed the physics metaphor in the 19th century: just as an elastic band stretches a lot or a little under force, demand 'stretches' a lot or a little under price pressure. Alfred Marshall is the economist usually credited with formalizing the concept of elasticity of demand in his influential late-19th-century economics textbook.