c.1300, "a shoot or twig," especially one for grafting, from Old French sion, cion "descendant; shoot, twig; offspring" (12c., Modern French scion, Picard chion), of uncertain origin. OED rejects derivation from Old French scier "to saw." Perhaps a diminutive from Frankish *kid-, from Proto-Germanic *kidon-, from PIE *geie- "to sprout, split, open" (see chink, n.1). Figurative use is attested from 1580s in English; meaning "an heir, a descendant" is from 1814, from the "family tree" image.