Sanku comes from the georgian სამკუთხედი (samk'utkhedi).
The reason it is based of georgian is because "ku" sounds like how slavic languages refer to shapes, and also sounds very similar to the major east asian languages refer to triangles.
A possible sitelen pona symbol would be 2 triangles in one another.
Reasons why this word would be useful would be to describe the colour glyphs and it could also be to be used to describe other more easily.