It's a clawspangler, part of the cable tension adjusting system on an early 80's era DC Grand Kahuna brake caliper. Threaded portion is keyed and goes into the half-circle end. Disk-shaped nut sits on the top of the other end with the cable socket above it. There's a rubber piece (which actually IS called a doohickey) that the threaded portion goes through in a slight interference fit that sits in the center section and keeps the nut from backing out.

Did a really poor job of maintaining cable tension, which lead to the elimination of the entire Kahuna product line, and eventually the financial implosion of DC and subsequent domination of the market by Shimano.

Sheesh. I thought you guys knew C&V.