from the GNU version of the Collaborative International Dictionary of English
- n. a system under which books, bulky manuscripts, etc., may be transmitted by mail.
from The Century Dictionary and Cyclopedia
- n. An arrangement in the British postal service by which books and printed matter other than newspapers, as well as manuscripts intended for publication, are conveyed at reduced rates of postage, when the wrappers are left open at the ends.
Sorry, no etymologies found.