Origin: NaPoM

It has yet to be confirmed, but sources indicate that NaPoM looks to be most likely be the inventor, or is atleast the person who got it out there. The sound is most powerfull on stage as shown by NaPoM in his GBB battles and eliminations. As you may notice if you watch the tutorials, the sound can be done in 2 different ways, but both are called and classified as the same.

The abbreviation for this sound is: Undecided