They spent a miserable day in this lonely and unpleasant country. Their camping-place was damp, cold, and uncomfortable; and the biting insects would not let them sleep. There were also abominable creatures haunting the reeds and tussocks that from the sound of them were evil relatives of the cricket. There were thousands of them, and they squeaked all round, neek-breek, breek-neek, unceasingly all the night, until the hobbits were nearly frantic.The next day, the fourth, was little better, and the night almost as comfortless. Though the Neekerbreekers (as Sam called them) had been left behind, the midges still pursued them.
The Fellowship of the Ring, Chapter 11, "A Knife in the Dark"
Is this some cute language that only twins understand, or what?
It's hobbit-talk that only hobbits and midges can understand :) See Fellowship Book I Chapter 11, "A Knife in the Dark", pp. 246-247 :)