What is "brown bill"

Brown bill \Brown" bill`\ [Brown + bill cutting tool.] A bill or halberd of the 16th and 17th centuries. See 4th Bill.

Many time, but for a sallet, my brainpan had been cleft with a brown bill.
--Shak.

Note: The black, or as it is sometimes called, the brown bill, was a kind of halberd, the cutting part hooked like a woodman's bill, from the back of which projected a spike, and another from the head.
--Grose.