One of the most famous papal encyclicals is Leo XIII’s Rerum Novarum (1891), about labor, capital, and social justice. I’m not going to go into either the theological or the historical implications of the speech; my interest here (and, frankly, my interest tout court) is solely in the title and its meaning. I was—”shocked” would be too strong a word; let’s say unhappy—to discover that the Wikipedia article begins: “Rerum Novarum (Latin for On the New Things)…” As I sputtered on the Talk page:
“Rerum novarum” does not mean “On the New Things”! To translate “res novae” by “new things” is like translating “hot dog” into French as “chien chaud.” “Res novae” is a fixed phrase or idiom meaning (to quote the Oxford Latin Dictionary) “constitutional changes, revolution.” That is what it has always meant in Latin, and that is how Leo is using it here: “Rerum novarum semel excitata cupidine, quae diu quidem commovet civitates…” is rendered (in the Wikisource translation) “That the spirit of revolutionary change, which has long been disturbing the nations of the world…” It should be translated “Of revolution” if it must be translated in the first line of the article. [...] Well, “Of revolution” is misleading—that could imply revolution is the topic of the encyclical, which it isn’t, it’s just the first two words. That’s why I wrote “if it must be translated in the first line”; it doesn’t make much sense to translate the first two words out of context.
Cicero says “rem publicam miscerent et rerum novarum causam aliquam quaererent”; Caesar says “cupiditate regni adductus novis rebus studebat”; in a lovely bit from the Novum Organum, Francis Bacon writes “Studia enim hominum in ejusmodi locis in quorundam authorum scripta, veluti in carceres, conclusa sunt; a quibus si quis dissentiat, continuo ut homo turbidus et rerum novarum cupidus corripitur”—if you disagree with the accepted authors in a school or academy, you are accused of being a turbulent revolutionary. This is a public service announcement: to translate a foreign language, it is not sufficient to look up each word in a pocket dictionary and string the results together.