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.
Siracusa Lemon
The European Union has nine (PGI) denominations for lemons: six of these are from Italy, one from France, one from Spain, and one from Portugal. Other than the "Siracusa lemon", the Italian denominations are the "Limone di Sorrento", the "Limone Costa d'Amalfi", the "Interdonato di Messina", the "Femminello del Gargano", and the "Limone di Rocca Imperiale". The French denomination is the "Citron de Menton". The Spanish denomination is the "Citricos Valencianos", while in Portugal the "Citrinos do Algarve" is protected.