Presume it's from the connection to death, as in the following. I think it must have been used to make coffins.
Come away, come away, death,
And in sad cypress let me be laid;
Fly away, fly away breath;
I am slain by a fair cruel maid.
My shroud of white, stuck all with yew,
O, prepare it!
My part of death, no one so true
Did share it.
Twelfth Night, Shakespeare