Avada Yodada!

"ARE YOU BOYS FIGHTING AGAIN?!"

Merlin's pants! 6 and 8YO Bronko and Nagurski are running all over the house, wands at the ready,  cursing each other... in their own unique way:

"AVADA YODADA!" 
"POOPEFY!" 
"AFARTA KADAVRA!"
"GLOPPIO!"
"IMPEDIMENTA BUTTSIO!"
"LOOGIA!"
"BARFAMENTI!"
"POOPMOS!"
"LEVIDORKUS!"
"ALOHA MAMA!"

Then Da-da stops them cartwheeling on the stairs and they say, "NOFUNDO."

Jeez. The wizarding equivalent of cowboys and indians, by way of Blazing Saddles.

[Btw, "avada kadavra" is actually Aramaic for, "let the thing be destroyed," originally meant to heal, as in, "let the illness be destroyed." It's also the etymological source of, "abracadabra," which Da-da guesses you already suspected; alas, the abracadabra curse can only make rabbits disappear and reappear. Of course, one might seriously need to consider the skeletal remains.]

Oops. Looks like someone used abracadabra again.

Of course, Viagra-maker Pfizer is now working 24/7 to copyright, "LEVIDORKUS."