In the Middle Ages a monastery on the island was dedicated to St Mary of Nazareth. Consequently, the name of the island was “Santa Maria di Nazareth”.
The name was probably too long to be practical, so in daily speech people shortened it to nazaretum.
This happened even before the establishment of the plague hospital on the island.
The neighbour island was (and still is) another monastery. Both the island and the Armenian monastery is called San Lazzaro degli Armeni.
Most likely people mixed up the two names, and the ‘N’ of nazaretum morphed gradually into the ‘L’ from Lazzaro (Lazarus), and we got lazaretum.
The ending -um which is very common in Latin, over time became -o in Venetian and Italian. That way we arrive at lazareto.
The Venetian language is not fond of double consonants, and tends to avoid them, or even reduce them to single consonants. Italian, on the other hand, likes double consonants very much, so in Italian we have the word lazzaretto.
Why does the English word Lazaret have single consonants? Because English didn’t acquired the word from Italian, but from Venetian.
The Venetian language was a commonly spoken language well into the 1800s. Venice was an obligatory stop on the Grand Tour for many young men of wealthy European families, and Venetian diplomacy was renowned all over Europe.
As such it is not odd that English acquired the word lazaret without the double consonants, because it came from the Venetian rather than from the Italian.
- Santa Maria di Nazareth
- Italian: Lazzaretto
- English: Lazaret