What is the X in X-mas?
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," 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.
develop de·vel·op (dĭ-věl'əp)
v. de·vel·oped, de·vel·op·ing, de·vel·ops
To progress from earlier to later stages of a life cycle.
To progress from earlier to later or from simpler to more complex stages of evolution.
To aid in the growth of; strengthen.
To grow by degrees into a more advanced or mature state.
To become affected with a disease; contract.