Non veni pacem mittere, sed gladium.
Knowing your fondness for all things nautical, I believe this is the corner of a sail, no?
It is the corner of a sail, and shows amazing hand work.
A beautiful solution to distribute point loads over a larger surface area. This probably evolved over time, driven by harrowing heavy sea scenarios.
That or maybe a sailor's hammock?
That's the way they were made before sewing machines. Beautiful work.