Citron
A source of confusion is that "citron" or similar words in French (and other languages), and English are false friends, as they refer to the lemon. Indeed, into the 16th century, the English name "citron" included the lemon and perhaps the lime as well.
Lemon Incest
The title is a play on words in French in the chorus between "Un zeste de citron" ("A lemon zest") and "Inceste de citron" ("lemon incest").