A cutlass is a short, broad sabre or slashing sword, with a straight or slightly curved blade sharpened on the cutting edge, and a hilt often featuring a solid cupped or basket-shaped guard. It was a common naval weapon. (www.wikipedia.com)
Most likely chosen by pirates because they were the preferred weapon of choice for sailors, etc.

Here are the caches you need: 2) GC5ATFO - GOLD HOOPS 3) GC5C2QW - CUTLASS 4) GC5ATGV - WE LOVE RUM 5) GC5D2FT - IN MEMORY OF PETIE 6) GC5B4Q1 - PIRATE GARB 7) GC5C2PY - MY PARROT FINAL STAGE - GC5D46R - TREASURE CHEST