Able seaman Vell was a Starfleet operations division crewman who served during the late 23rd century. (Star Trek VI: The Undiscovered Country)
Vell's name comes from the name tag that was included along with a Starfleet radiological suit sold on It's A Wrap! sale and auction. [1]
He was played by one of several unknown actors who served aboard either the USS Enterprise-A or USS Excelsior.