Osanwe-kenta was an essay published in the journal
Vinyar Tengwar. You can purchase individual issues for cheap here:
Vinyar Tengwar
As for your Goldberry theory: bleh. Why is Maia (or Maia-hybrid) the catch-all race for beings whose origins aren't fully explained? Like that ridiculously tenuous Beorn theory linked to above.
[ April 30, 2003: Message edited by: obloquy ]