Green’s Dictionary of Slang

1. free of charge; also attrib. see cite 1848.

1848		Southern Reporter (Cork) 20 July 1/2: An editor out West walks into the affections of his ‘dead-head’ suscribers in the following genteel style: [etc].
1865		Leaves from Diary of Celebrated Burglar 37/1: Tom’s waiter, who had been ‘colloring [sic] his lush’ all the evening on the dead-head system.
1873		Winfield Courier 27 May 1/6: A couple of lads in Portage City, Wis., climbed a tree outside the tent to get a ‘dead-head’ view of Forepaugh’s circus [DA].
1880		Bulletin (Sydney) 30 Oct. 9/1: The ‘dead-head’ element was in great force.
1882		Nat. Police Gaz. (NY) 9 Sept. 3/2: [I]t will be impossible for us to get dead head tickets from Abbey after telling the truth about him.
1884		Sporting Times 4 Oct. 1/1: The British Association can go on a big dead head bust around Canadad.
1892		Congressional Record 31 May Appendix 385/1: The free-delivery service is burdened by the collection and delivery of thousands of dead-head matter under the ‘penalty postage system’ [DA].
1900		Sydney Sportsman (Surry Hills, NSW) 17 Oct. 1/3: Another Tommy, by way of a gee, said it was a dead head ticket for a tea fight.
		:
1904		Sun. Times (Perth) 7 Feb. 5/4: The annual shivoo came round and the party politicians were carefully omitted from the dead-head list.
1908		D.G. Phillips Old Wives for New 219: Probably Murdock, with his special car, was traveling deadhead. We other people paid our fare.
1948		Time 23 Aug. 63/3: Rickenbacker thinks he knows what is wrong with the industry: too many carriers, too low fares, too many deadhead services [DA].

2. (also deadheaded) useless, spec. non-participant.

1918		C.J. Dennis ‘A Guide for Poits’ in Backblock Ballads 39: It’s easy fer to pen a sweet refrain / Wiv this ’ere jist a dead-’ead sort o’ line.
1973		G.V. Higgins Digger’s Game (1981) 37: They got a deadhead bunch and they made about sixty dollars.
1993		R. Shell Iced 17: The dead-headed tight-assed nerks that made up most of Columbia University’s student world.