A French medieval form of Isabel, ultimately from Hebrew Elisheba, meaning God is my oath.
Isabeau is the medieval French form of Isabel, itself a Provençal and Iberian variant of Elizabeth, which traces back to the Hebrew Elisheba — meaning "my God is an oath" or, in a richer reading, "my God is abundance." The name traveled through the Iberian Peninsula before being softened into the French court's preferred vowel-rounded form, acquiring an elegance that made it a favorite among European nobility during the high and late Middle Ages. The name's most prominent historical bearer is Isabeau of Bavaria (1370–1435), Queen of France as the wife of Charles VI.
She was one of the most powerful and controversial women of her age — a regent who navigated the catastrophic Hundred Years' War and the madness of her husband, signing the Treaty of Troyes in 1420 that briefly disinherited her own son in favor of the English crown. Historians have debated her motivations across centuries, and her legacy remains vigorously contested, but her name became indelibly associated with royal ambition and medieval political intrigue. Isabeau faded from everyday use as Isabella and Isabel rose in popularity during the Renaissance, but it has never fully disappeared.
It lingered in French literature and historical fiction as a marker of medieval authenticity, and has enjoyed a romantic revival in the twenty-first century among parents seeking a name with the warmth of Isabel but a more rarefied, antiquarian feel. The 1985 fantasy film *Ladyhawke*, featuring a character named Isabeau, helped cement the name's dreamy, otherworldly associations for a generation of parents.