How far back can you trace this slang?  Urban dictionary says ‘40 or ‘50s. I remember it was popular slang among GIs returning from the Pacific.  Just chatting with someone born in 1970 who never heard it - he says.

OED has it from 1888.

HDAS has “nail in my coffin” from 1867. It also has “Here’s another nail in your coffin” in Bret Harte’s 1873 Skagg’s Husbands, although that may be reference to liquor. Some of the early uses may be references to cigars rather than cigarettes.

Not an antedate, but I enjoyed this squib from The Sanitarian, Vol. 24 (1890), p. 147, and thought I’d share it:

Coffin Nails.—In some parts of the West cigarettes are quite commonly referred to as “coffin nails.” This is by some considered unjust to coffin nails, which are, in their way, useful and even necessary articles.