If an 8-sided shape is an octa-gon octa meaning 8,
A 7-sided shape is called a hepta-gon, hepta meaning 7,
A 6-sided shape is a Hexa-gon, hex meaning 6,
And a 5-sided shape is a penta-gon, penta meaning 5,
Then why is 4-sided shape called a square and not a quadrigon? And a 3-sided shape called a triangle instead of a trigon? And a 2-sided shape called a line instead of a duogon?