Fleur is the French word for “flower,” and its history stretches all the way back through Latin to a very old Indo-European root.

The lineage

*Proto-Indo-European → bʰleh₃- The trail starts with the reconstructed root *bʰleh₃-, meaning “to bloom” or “to flourish.” This same root eventually gives English words like bloom, blossom, and flourish — so fleur and flourish are, in a sense, distant cousins.

Latin → flōs, flōris From that root, Latin developed flōs (nominative) / flōris (genitive), meaning “flower.” This is also the source of many other flower-related words across Romance and English:

• flora (plant life)
• floral
• flourish
• deflower, effloresce

Old French → flor / flur As Latin evolved into Old French, flōs/flōris became flor or flur. Old French tended to simplify Latin’s case endings, keeping something close to the stem.

Modern French → fleur By the time French stabilized into its modern form, flor had shifted to fleur, with the diphthong “eu” replacing the earlier “o.” This is a fairly common sound change in French — Latin short “o” in certain positions often became “eu” (compare Latin cor → French cœur, “heart”).

Where it shows up in English

English borrowed fleur directly in a few places, often keeping a French flavor:

• Fleur-de-lis — literally “flower of the lily,” the stylized lily emblem associated with French royalty and heraldry.
• Fleuron — a flower-shaped ornament, used in typography, pastry, and design.
• As a given name — Fleur is used directly as a first name in English and French alike (popularized in English partly through the character Fleur Delacour in the Harry Potter series).

Quick summary

Stage	Form	Meaning
Proto-Indo-European	bʰleh₃-	to bloom
Latin	flōs/flōris	flower
Old French	flor/flur	flower
Modern French	fleur	flower

So when you say fleur, you’re using a word with roughly 6,000 years of continuous meaning behind it — “to bloom” all the way down.