Ennui
mid 18th century: French, from Latin in odio(n- ), from mihi in odio est ‘it is hateful to me’. Compare with annoy.
wiktionary
Borrowed from French ennui, from Old French enui(“annoyance”), from enuier (modern French ennuyer), from Late Latin inodiō, from Latin in odiō(“hated”). Doublet of annoy.
etymonline
ennui (n.)
1660s as a French word in English; nativized by 1758; from French ennui, from Old French enui "annoyance" (13c.), back-formation from enoiier, anuier (see annoy). Hence ennuyé (adj.) "afflicted with ennui," and thence ennuyée (n.) for a woman so afflicted.
So far as frequency of use is concerned, the word might be regarded as fully naturalized; but the pronunciation has not been anglicized, there being in fact no Eng. analogy which could serve as a guide. [OED]
