Green’s Dictionary of Slang

deader n.

(orig. US)

1. an exhausted person.

[UK]Farmer & Henley Sl. and Its Analogues.
[US]W.C. Gore Student Sl. in Cohen (1997) 9: deader. n. A weary, or exhausted person.
[US]Times Dispatch (Richmond, VA) 9 Dec. 4/5: See that medder? / I’ve tramped it till I’m sore. / To find as I’m a deader, / It’s a moor.

2. a dead person, a corpse; thus be a deader, to be recently dead.

[Aus]‘Rolf Boldrewood’ In Bad Company 22: They’d be deaders the first dry season – down from weakness for a week or two, with their eyes picked out by the crows.
[UK]‘Taffrail’ Pincher Martin 292: ’Ere [...] one o’ them ’ere deaders ’as come back ter life!
[US]L. Pound ‘American Euphemisms for Dying’ in AS XI:3 198: Is a deader.
[UK](con. 1930s) D. Behan Teems of Times and Happy Returns 98: The deader is goin’ to start walking now and I’m glad I’m in the middle between Seamus and Brian.

3. (Aus.) a murderer.

[Aus]P. Temple Truth 61: Knowing the dead’s a step, catching the deaders, that’s the trick.