quell [kwɛl]
vb (tr)
1. to suppress or beat down (rebellion, disorder, etc.); subdue
2. to overcome or allay to quell pain to quell grief
[Old English cwellan to kill; related to Old Saxon quellian, Old High German quellen, Old Norse kvelja to torment]
queller n
1.Put an end to (a rebellion or other disorder), typically by the use of force: "extra police were called to quell the disturbance".
2.Subdue or silence (someone): "Connor quelled him with a look".
Quell is an app for iPad and iPhone that is "a charming zen puzzler that is sure to test your brain and capture your heart!" The objective is simple: slide a droplet around a layout of obstacles, traps and pathways, until you have collected all the pearls. Underneath this simple gameplay lies a world of intricacy!
If memory serves me correct, to quell something means to stop something, to put it bluntly. You know, put an end to things.
I know this because I heard it on Halo 2. And I have played that game so many times (because I have only a few games on my uncles old xbox T_T) that I know the quote XD "Be silent and swift, and we shall quell this heresy without incident." And I do believe the level is called 'The Arbiter"