Call then Wrap-pins or Scar-pins, they beat cotter pins.

Or ring clips. These make the process of retuning your rig easy enough to do more often. Plus they neaten the turnbuckles without needing fancy covers.
The original Scar Pins come from the racers at APS and the pricier Wrap Pins are made by C.S.Johnson and sold most everywhere. Either way, they are just cotter pins epoxied to Velcro strips.