Bluefin naming: "handle" or "capability"?

I quite like capability when referring to the effect system members and handles when talking about the what the function requires to provide the effect.

Reading the type signature for fooBf, I read it as:

"fooBf is a computation in which capability e is a member of the capabilities es and it takes a handle to an IOE over capability e and produces an Effect using the capabilties found in es to produce the return value r.”