Twig asked me about the origin of the phrase "cold turkey." I didn't know, so I looked it up.
No info at Quinion's World Wide Words, which is my most trusted source for etymology these days.
No etymology info in MW11 (abridged) or MW3 (unabridged). But MW3 does give a couple of interesting definitions from before its use regarding drugs; those definitions have to do with being blunt and/or something being a certainty or sure thing. I can imagine those definitions morphing into the modern sense. First cite of the modern sense (in MW11) is 1921.
The Online Etymology Dictionary says:
"without preparation," 1910; narrower sense of "withdrawal from an addictive substance" (originally heroin) first recorded 1921. Cold turkey is a food that requires little preparation, so "to quit like cold turkey" is to do so suddenly and without preparation.
Color me dubious.
The etymology derives from the phrase talk turkey, in which someone deals matter-of-factly with a subject. Some, however, believe the derivation is from the comparison of a cold turkey carcass and the state of a withdrawing addict--most notably, the cold sweats and goose bumps. [...] Yet another suggestion of origin is that cold turkey is a dish that needs little or no preparation. "To quit like cold turkey" would be to quit in the same way a cold turkey is served, instantly just as you are without preparation.
In other words, Wikipedia isn't sure.
1915-20, Americanism; prob. from the phrase to talk cold turkey to speak bluntly about something unpleasant, var. of to talk turkey; see turkey
I don't normally put much faith in dictionary.com, but it does seem to be more or less in accord with MW3 unabridged on this, and this answer seems much more plausible to me than the "little or no preparation" or "turkey carcass" versions.