"The mouse does not sleep at night."
Translation:Mus noctu non dormit.
Noctu gave "nocturne" in French, "nocturno" in Spanish, "notturno" in Italian (where we see the "n..t" pattern, same than in the French nuit),
French Nocturnal (from nocturne or from Latin nocturnalis) was borrowed in English. The French "diurne", (and derived diurnal) for "of the day" wasn't borrowed.
Night also have a similar pattern (see Italian notturno and French nuit), but is from West Saxon neaht, Anglian næht, neht. It's a common PIE root between Saxon and Latin.