Why is the ninth month called September?
late 13c., "unfurl" (a banner, etc.), from Old French desploiir (Modern French déployer) "unfold, unfasten, spread out" (of knots, sealed letters, etc.), from Latin displicare "to scatter," from dis- "un-, apart" (see dis-) + plicare "to fold" (see ply (v.1)).
Properly of sails or flags (and unconnected to play); meaning "reveal, exhibit" is late 14c. Related: Displayed; displaying.
1580s, "description," from display (v.). Meaning "exhibition" is from 1680s.