Old English openung "act of opening" (a door, mouth, etc.), "disclosure, manifestation," verbal noun from present participle of open, v.. Meaning "vacant space, hole, aperture, doorway" is attested from c.1200. Meaning "act of opening (a place, to the public)" is from late 14c. Sense of "action of beginning (something)" is from 1712; meaning "first performance of a play" is 1855; "start of an art exhibit" is from 1905. Sense of "opportunity, chance" is from 1793.