Where does the French word “bonheur” come from?

Le bonheur is happiness, and it is built from two pieces: bon, “good,” and heur, an old French noun meaning luck or a favourable omen. The original sense was therefore closer to good fortune than to contentment. Its mirror image survives alongside it — le malheur, misfortune — and so do the adjectives heureux and malheureux, from the same root.

Heur came from Latin augurium, an omen read from the flight of birds, and was written eür with no h until around the 14th century, when the spelling drifted towards heure (“hour”) — a look-alike it is not actually related to. Today heur survives almost only in the formal avoir l’heur de, “to have the good fortune to.”