Chanak was a 23rd century Starfleet operations division crewman who was at some point promoted from petty officer, 2nd class to petty officer, 1st class. (Star Trek films)
Chanak's name comes from the name tag that was included along with two Starfleet uniform and accessory lots sold on It's A Wrap! sale and auction. [1] [2] There was no indication in which film it was specifically used, however, like most other items of this type it was presumably both Star Trek II: The Wrath of Khan and Star Trek VI: The Undiscovered Country.