From Latin 'displicare' (to unfold) — to deploy is to spread what was folded into active position. A doublet of 'display.'
To move troops or equipment into position for military action; to bring into effective use; in computing, to make a system or application operational.
From French 'déployer' (to unfold, to spread out, to display), from Old French 'desploier' (to unfold), from Latin 'displicāre' (to scatter, to unfold, to spread apart), composed of 'dis-' (apart, in different directions) and 'plicāre' (to fold, to fold together), from PIE *pleḱ- (to plait, to fold, to weave). To deploy troops is literally to 'unfold' them — to take a compact marching column and spread it out into an extended battle line, unfolding the force like a fan. The same PIE root *pleḱ- gives 'complex' (folded
Software engineers borrowed 'deploy' from the military in the 1990s, and the metaphor maps perfectly: military deployment 'unfolds' troops from storage (barracks) into active positions (the field), while software deployment 'unfolds' code from a repository into production servers. Both senses preserve the Latin idea of taking something folded up and spreading it out for use.