This story is also recounted in Katherine Briggs' A Dictionary of Fairies,
where the writer states that it is perfectly good Greek. Kind of in synch
with the thought of the time that all good faery folk should speak a
classical language.
Mike
>
> "The twelve-year-old Welsh schoolboy Eliodor, who claimed to have visited
the
> underworld in the early twelfth century, alleged that he learnt its speech
> and used to repeat it to his listeners. Years later, Gerald of Wales
recorded
> two of his phrases, 'Ydor ydorum' ('Bring water') and 'Halgein ydorum'
('Bring
> salt')."
>
> I presume that would be among the earliest conlangs of which we have some
> record.
>
> Doug