ces,Ralph's version is more true to the original by my memory. I do still think it's "My belly is a'achin' there's a shakin' in my head." It's a better line lyrically.
Codeine is a narcotic (sleep inducing) drug. It is derived from the opium poppy just as are heroin and morphine. Codeine is a very effective cough suppressant and therefore was a primary ingredient in cough syrups in the 1800's. It continued in use for some time in the US despite the furor over narcotic drugs in general. In the State of Maryland in the 60's you could buy codeine based cough syrups at the pharmacy, but you had to sign for them. The idea was to keep track of people who's coughs may be too strong or last too long.
It was a legal way to maintain an addiction, but it was not cheap, and oral ingestion is a poor way to get a drug into your system. It is very slow, so it does not provide the "rush" that many addicts seek. Robitussin (sp?) cough syrup was also abused in the past when it had codeine in it.
Although Codeine is not a popular drug of abuse in the US, I like this song because it provides a pretty good insight into the addict mind without being overly preachy.
I believe I read in Sing Out decades ago that Buffy agreed the last line could be reel or real depending on your taste. Besides, how will your audience know?
Roger in Baltimore