How would a courtier of the Ancien Régime have translated the phrase "Her Illustrious Highness"?

Question

I'm trying to find the best translation for the Russian term Сиятельство. (I can't speak Russian either! So don't expect too much from me in that regard.) This is a form of address, often translated into English as Illustrious Highness. In the old Russian Empire, it was the default form of address for princes and princesses not part of the imperial family. (With the tsar's blessing, some princely families used the higher style of Serene Highness, but let's not get into all that!)

The literal translation of Her Illustrious Highness would, I think, be Son altesse illustre. However, I know from the Monégasque princely family that their style - the official English form of which is His/Her Serene Highness - is Son altesse sérénissime, and not Son altesse sereine. Might Son altesse illustrissime then be a more elegant translation? Or is that just nonsense?

Answer 1

I don’t have too much knowledge of historical context around it, but having grown up for a large part of my life in a French environment (France !) I’m almost positive the word majesté (literally « majesty ») is the best word to associate with « illustre », in terms of frequency of use.

Though the Monégasque princely family seems to be using a similar phrase, your idea of using son altesse illustrissime sounds mostly like a humorous exaggeration to a mere mortal, while son altesse illustre could probably work if you instead said « illustre altesse » (French can also have adjectives before the noun, when the sentence is respectful or as a way to make it elegant). However, I think « illustre majesté » is best because the adjective contains 2 syllables, versus 3 for the noun, allowing it not to be overshadowed. But perhaps I’m missing a semantical difference that leaves « altesse » as being a better word choice.

Also, « Son » and « Votre » can be used interchangeably (unsure which is most respectful though).