From Shakespeare's King Henry VI.
CADE: Brave thee! ay, by the best blood that ever was
broached, and beard thee too. Look on me well: I
have eat no meat these five days; yet, come thou and
thy five men, and if I do not leave you all as dead
as a doornail, I pray God I may never eat grass more. (see: http://phrases.shu.ac.uk/meanings/38250.html)