Ennui is weariness caused by having nothing that interests you. A settled ennui.
It is not tiredness or sadness but flatness, which is why English kept the French word. Ennui is a doublet of annoy, since both come from a Latin phrase about being hated.
1nounennuiWeariness caused by having nothing that interests you.
“The ennui of that last summer runs through the whole book.”
ennui is a feeling.
French ennui comes from Latin in odio, in hatred; it is a doublet of annoy.
Latin
inodiō
Old French
enui — annoyance
French
ennui
English, today
ennui
From ennui. French ennui, from Old French enui (“annoyance”), from enuier (modern French ennuyer), from Latin inodiō, from Latin in odiō (“hated”). a doublet of annoy.
Etymology from Wiktionary, CC BY-SA