2. Listlessness and dissatisfaction resulting from lack of interest; boredom.
3. Etymology: from French, from Old French enui, from ennuier, "to annoy, to bore", from Vulgar Latin inodiare, from Latin in odio (esse), (to be) odious; in, "in" + odio, ablative of odium, "hate".
The phrase mihi in odio est, literally translated as "to me in a condition of dislike or hatred is"; meaning, "I hate or dislike", gave rise to the Vulgar Latin verb -inodiare, "to make odious", the source of Modern French ennuyer, "to annoy, to bore".
In the Old French period a noun meaning "worry, boredom", came from the verb ennuier. This noun in its Modern French form ennui was borrowed into English in the sense "boredom", the English word being first recorded in 1732.
People might have needed a word for boredom in the polite, cultivated world of the 18th century, but during an earlier period, about 1275, the English language had already borrowed the French verb ennuier, the source of our word "annoy".
This noun (ennui), with the sense “boredom,” was borrowed into English in the 18th century, perhaps filling a need in polite, cultivated society. One of the earliest instances of annoy in English is, in fact, used in the sense of "to bore an audience."