What is Head Money?

Legal Definition
A sum of money reckoned at a fixed amount for each head (person) in a designated Class. Particularly

(1) a capitation or poll tax.

(2) A bounty offered by the laws of the United States for each person on board an enemy's ship or vessel, at the commencement of a naval engagement, which shall be sunk qr destroyed by a ship or vessel of the United States of equal or inferior force, the same to be divided among the officers and crew in the same manner as prize money. In re Farragut, 7 D. C. 97. A similar reward is offered by the British statutes.

(3) The tax or duty imposed by act of congress of Aug. 3, 1882, on owners of steamships and sailing vessels for every immigrant brought into the United States. Head Money Cases, 112 U. S. 580, 5 Sun. Ot. 247, 28 L. Ed. 798.

(4) A bounty or reward pnid to one who pursues and kills a bsndit or outlaw and produces his head as evidence; the offer of such a reward being popularly called "putting a price on his head."
-- Black's Law Dictionary
Legal Definition
A gratuity distributed among a ship’s officers and crew in the same manner as prize money. See 7 D. C. (U. S.) 97.
-- Ballentine's Law Dictionary