Facts in Candide
Westphalia, a region in Germany situated between the Rhine and Weser rivers. In 1648, it was the site of the Peace of Westphalia, the treaty that ended the Thirty Years' War. In 1758, a year before Candide was published, Duke Ferdinand of Prussia drove the French from Westphalia during the fighting of the Seven Years' War.
In 18th Century Europe, guns were generally larger, bulkier, and less wieldy, taking fewer rounds of ammunition and requiring a great deal of time to load. The "bullets" of Prussian guns were in fact small balls of lead that were shot like pellets at a target. Their results were analogous to those of modern bullets.
In Prussia in the 18th Century, the unit of currency was the "Thaler," a variant of the German Reichsthaler, which used a different fraction of silver in its minting. The "crown" was a form of British currency in use at the time of this translation into English and was not likely to have been seen in a Prussian inn at that time.
Historical records prove this statement wrong. In fact, all of these societies fell victim to venereal diseases early in their development. It is true, however, that the incidence of STDs in these countries, and in particular in Japan, has been significantly lower than in Europe, which may be due in part to their differing attitudes toward sex.
Porto is a city in northwest Portugal, about three hours north of Lisbon. It's sometimes called "Opporto" because traders who didn't speak Portuguese misinterpreted the phrase "O Porto" (of Porto) as "Opporto," assuming that this was the name of the city. Voltaire uses both to enhance the comedic effect of the Familiar having to call for wine (presumably because he finds Pangloss' argument tiresome).
These are all saints deified in the Roman Catholic Church. Our Lady of Atocha watches over the people of Madrid, St. Anthony of Padua is the patron saint of lost or stolen items, and St. James of Compostella is the patron saint of pilgrims. The old woman has effectively characterized Candide as a lost pilgrim, although where he's going and what he believes in is in question.
The Jewish Sabbath, as opposed to the Christian Sabbath, occurs on Saturday instead of Sunday. It is observed from sunset on Friday to nightfall on Saturday, which means that Don Issachar's arrival can be timestamped at sometime after supper but before the first stars came out. (There is, of course, a lewd suggestion to the fact that he has come only at night and not earlier in the day.)
A port city in Southwestern Spain, on the Atlantic coast. Its climate is said to be very temperate, and it has the added bonus of being in a different country with different extradition laws, making it possible for Candide to avoid prosecution for these two murders (despite one of them being, arguably, in self-defense).
A reference to Galilee, a city in northern Israel where Jesus Christ was said to have lived for the first thirty or so years of his life. Jesus's ministry was housed there, and many of his works take place around the Sea of Galilee. To call Cunegonde a "Galilean" in this derogatory way is to call her a Christian.
The Jewish people were enslaved in Babylonia in the Sixth Century B.C.E. This is one of the earliest examples of Anti-Semitism and set the stage for later and more drastic instances of persecution, such as the Holocaust. For Don Issachar to be the most choleric Jew since this captivity means that he's almost as angry as people were when they were enslaved.
Salah, one of the five pillars of Islam, dictates that every Muslim must pray to Allah five times per day at prescribed times, as mandated by the prophet Muhammad in the Quran, the holy book of Islam. Voltaire reminds us of the piety and discipline of this practice to contrast it with the horror and the bloodshed the Muslims inflict, thus building on the theme of religious hypocrisy central to the book.
An inversion of traditional Christian theology, which states that God is everywhere and in everything, including humans beings. This idea is expressed in Luke 17:21, "Behold, the kingdom of God is within you." Here, Martin says that the Devil is in everyone and everything, which underscores his dualist philosophy that evil is as prevalent as good.
Raphael, a painter and sculptor of the High Renaissance in Italy, most famous for his painting The School of Athens and for his portraits of the nobility, which are described here as being too dark and (so the collector thinks) anatomically inaccurate. It's possible that the darkness described here comes from the deterioration of the paint, which needs to be restored periodically. For instance, the paintings in the Sistine Chapel were darkened by smoke for centuries until they were restored to their original grandeur in the 1980s and 1990s.