1650s, "unroll, unfold," from French développer, replacing English disvelop (1590s, from Middle French desveloper), both from Old French desveloper "unwrap, unfurl, unveil; reveal the meaning of, explain," from des- "undo" + veloper "wrap up," which is of uncertain origin, possibly Celtic or Germanic. Modern figurative use is 18c. The photographic sense is from 1845; the real estate sense is from 1890.