The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: An English unit of mass equal to 12 slugs (386.088 pounds-mass), that accelerates by 1 inch per second squared (1 in/s²) when a force of one pound-force (lbf) is exerted on it. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.