Slaw bed

Does anyone know the origin of "slaw bed"? It looks like the forerunner of our Murphy bed but was probably used around 1700.

Do you mean to say that you have seen a picture, or have a reference from around 1700? Some context would help, to save me from the awful disgrace of saying the phrase conjures up the picture of a bed of cabbage. SS

I've looked in my references, especially regional slang, and haven't found anything.