It is mimicing the sound of a semi-automatic going off.
much like a little kid saying "pee-yowm" to indicate the sound of a pistol.
"You must create a weapon that can hit every point in space and time in the multiverse... with bullets that are each composed of every point in space and time in the multiverse... at point blank range to every point in space and time in the multiverse... And to clarify, the term "multiverse" includes: all alternate realities, parallel realities, perpendicular realities, potential realities, imagined realities, unimagined realities, inconceivable realities, and impossible realities. So you need a gun that shoots at everything, with everything, when next to everything. Now... how can we achieve *dramatic chord* too much dakka?"
All flight officers (in low-toned unison): "Dakka-dakka-dakka-dakka-dakka..."