Isabelle is the French form of Isabel, which developed from Elizabeth in medieval Spain and Provence and means "God is my oath" or "pledged to God". The French spelling gives the name a softer, more romantic look than Isabella or Isabel. Isabelle ranked 144th in the United States in 2000, entered the top 100 in 2005, peaked at number 79 in 2007 and ranks 166th in 2025.