I think field is, because a single class can have both constructor params and fields, and they can be named the same.
```
class Foo {
  @Inject String foo;
  public Foo(Integer foo) { }
}
```
Why you'd want to do that is beyond me, but it's valid java and not, technically, a conflict. I'm ok with f_foo and p_foo, but this was precise, what it meant, etc. 

The constructor version is `parameter_blah = ...` and I think it distinguishes things nicely for later maintenance.