Ennui

[ahn-wee, ahn-wee; French ahn-nwee] /ɑnˈwi, ˈɑn wi; French ɑ̃ˈnwi/

noun
1.
a feeling of utter weariness and discontent resulting from satiety or lack of interest; boredom:
The endless lecture produced an unbearable ennui.
/ˈɒnwiː; French ɑ̃nɥi/
noun
1.
a feeling of listlessness and general dissatisfaction resulting from lack of activity or excitement
n.

1660s as a French word in English; nativized by 1758; from French ennui, from Old French enui “annoyance” (13c.), back-formation from enuier (see annoy). Hence ennuyé “afflicted with ennui;” ennuyée 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]