What is this called? I would say it is a shackle or I suppose, a turnbuckle, but it appears to have a right threaded rod on both sides and right threaded free nuts inside.
I would just say it's a shackle or maybe a swivel, but there are some really important design properties that aren't specified by that. I want to say something that is usually about 5 to 1 length width aspect ratio, has a hole in both ends, has a wide berth for inserting and tightening free nuts and seems to have some kind of in the field bending and maneuverability capability.