de·vel·op / diˈveləp/ • v. (-vel·oped, -vel·op·ing) 1. grow or cause to grow and become more mature, advanced, or elaborate: [intr.] motion pictures developed into mass entertainment | [as adj.] (developing) this is a rapidly developing field | [tr.] entrepreneurs develop their skills through trial and error. ∎  [intr.] [often as adj.] (developing) (of a poor agricultural country) become more economically and socially advanced: the developing world. ∎  [tr.] convert (land) to a new purpose by constructing buildings or making other use of its resources. ∎  construct or convert (a building) so as to improve existing resources. ∎  [tr.] elaborate (a musical theme) by modification of the melody, harmony, or rhythm. ∎  [tr.] Chess bring (a piece) into play from its initial position on a player's back rank. ∎ Geom. [tr.] convert (a curved surface) conceptually into a plane figure as if by unrolling. ∎  [tr.] Math. expand (a function, etc.) in the form of a series.2. start to exist, experience, or possess: [intr.] a strange closeness developed | [tr.] I developed an interest in law | [tr.] AIDS patients often develop a rare type of cancer. 3. [tr.] treat (a photographic film) with chemicals to make a visible image.

develop unfold, lay open (more fully). XVII (first as pp. developed; preceded by †disvelop (XVI–XVIII).- OF. desveloper, mod. développer :- Rom. vb. f. L. DIS- 2 + *volup-, *velup- (ult. orig. unkn.).
So development XVIII.