I have no idea where that phrase came from, but it was not from Latin. The word for
night is
nox (genitive
noctis).
"Lovers of French literature may remember the immediate source for Mozart's opera, Pierre-Augustin de Beaumarchais's anti-feudalist comedy,
Le mariage de Figaro (1785), in which Beaumarchais' alter ego, Figaro, attacks the
ius primae noctis in words that Braveheart could have spoken to his English oppressors and that audiences in revolutionary France as well as their contemporary counterparts would enthusiastically support"
http://www.fu-berlin.de/phin/phin31/p31t4.htm