1976, David Edgar, Saigon Rose, Act II, Scene 4, in Plays: One, London: Methuen Drama, 1987, p. 215, It’s a poem, students learn, about the symptoms of syphilis. I once had an affairette with a final year medic from Inverness who used to mumble it all the time, often at the most inopportune moments.
Source: wiktionary