Forgive my pasting from my ten buck CD dictionary:
ran[som 7tran4s!m8
n.
5LME traunsom, prob. altered < L transtrum, crossbeam, lit., that which is across < trans: see TRANS36
1 a crosspiece in a structure; specif., a) a lintel b) a horizontal crossbar across the top or middle of a window or the top of a door
>2 a small window or shutterlike panel directly over a door or window, usually hinged to the TRANSOM (sense 1b)
3 any crosspiece; specif., a) the horizontal beam of a gallows or cross b) any of the transverse beams attached to the sternpost of a wooden ship c) the transverse, aftermost part of a boat with a square stern
over the transom by unsolicited submission, as to a publisher: said of a manuscript, etc.

I did it mostly because I got a laugh out of the last phrase, about submitting a manuscript by throwing it through the transom window of the editor's locked door.