Отрок же не знал ничего; только Ионафан и Давид знали, в чём дело.
(The boy knew nothing about all this; only Jonathan and David knew.)
But the boy knew nothing. Only Jonathan and David knew the matter.
But the lad was not aware of anything; only Jonathan and David knew about the matter.
He, of course, suspected nothing; only Jonathan and David understood the signal.
But the lad knew not any thing: only Jonathan and David knew the matter.
But the lad did not know anything. Only Jonathan and David knew of the matter.
And the lad knew nothing: only Jonathan and David knew the matter.