A QumpIn was a Klingon title and position for those that worked within the Klingon Empire. It was the equivalent of a starship's communications officer. (tlhIngan Hol reference: The Klingon Dictionary, ST reference: Klingon Bird of Prey Owners' Workshop Manual)
In the mirror universe, Regent Worf, while on the IKS Negh'Var demanded from his QumpIn to be put in communications with the port authority at Khitomer. After the assassination of his best friend Duras, Worf left the QumpIn to command the Negh'var while he determined his friend's death. (DS9 novel: Dark Passions)