Better yet why not call a quadrilateral a qaudriangle? Or maybe Quadrigon?
A five sided object is can also be called a Pentalateral can also be a Pentangle?
How does maybe a Triagigon or Trigon sound for triangle?
Hexagon can also be a Hexiangle or Hexerlateral!
The famous Octagon, American Stop, Sign can also be called an Octiangle or a Octalateral!
There is the theoretical closed Biangle that only exists in high dimensions or rather the Bilateral. Closed Biangles shapes don't exist in our universe, except for maybe Pac-Man's tunnel.
Maybe Diangle, Diagon, or Dilateral is better?
Likewise there is the invisible Monoangle which can be called a Monogon or Monolateral, and you have to be in "God-Mode" to understand that. Unigon, Unilateral, and Uniangle are additional names for the Monogon. They really do exist, more so than the Great Pumpkin.