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.
Kitron
Kitron is a citron liqueur produced on the Greek island of Naxos. It is made from the fruit and leaves of the citron tree, which is similar to the lemon tree but stronger and slightly different in taste.