According to the Elisabeth Vincentelli (whose article “You Are What Your Name Says You Are” was recently published in the New York Times), the big baby-naming trends in France are the letter “a” for girls (Clara, Sarah, Léa) and the letter “o” for boys (Mathéo, Enzo, Hugo).
Vincentelli also notes that, according to sociologist Philippe Besnard,
Until the 1970s the popularity of names trickled down from the upper classes. For instance, “Gilles” peaked in France’s high-society registry in 1942 and in the general population in 1960. That all changed in the 1980s, when the less wealthy and less educated turned into first-name innovators (perhaps caught up in fads spread by popular music and TV) while the rich rediscovered more traditional French-sounding names.
(Thank you to Nancy Friedman of Away With Words for letting me know about the article.