To develop something is to unwrap it. The word comes from French développer — 'to unfold, to reveal' — from Old French desveloper, composed of des- ('un-') and voloper ('to wrap up'). Development, in its oldest sense, is the removal of wrapping.
The metaphor is powerful and precise. A seed develops into a plant by unfolding what was always inside it. A child develops by revealing capacities that were latent. A story develops as the author unfolds the plot. In every case, the thing being developed was already there — it just needed unwrapping.
Photography captured this meaning perfectly. When a photographer develops film, the image is already on the negative — chemicals merely reveal it. The darkroom is a place of unwrapping.
The opposite of develop is envelop — to wrap up. The two words are mirror images built from the same root. An envelope wraps a letter; development unwraps potential. French still treats them as a matched pair: envelopper and développer.
The Spanish cognate desarrollar follows the same logic but uses a different wrapping word — arrollar ('to roll up'), so desarrollar means 'to unroll'. The Italian sviluppare is closer to the French model.
The word's journey from physical unwrapping to abstract growth happened during the Enlightenment, when thinkers began speaking of the development of ideas, societies, and human understanding — all things that unfold over time.