Green’s Dictionary of Slang

Emily Post n.1

[rhy. sl. = ghost n. (7); ult. author of popular etiquette manual Emily Post (1872/3–1960)]

(Aus.) a creditor.

[Aus] ‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxiv 4/5: emily post: A dun, or one who is owed money.
[Aus]R. Aven-Bray Ridgey-Didge Oz Jack Lang 27: Emily Post One to whom money is owed (ghost).