Chouquettes are small choux pastries with pearl sugar. The choux pastry dated from the 16th century and was invented by the Italian Popelini who was the pastry cook of the French Queen Catherine de Médicis (1519-1589). In 1760, Jean Avice (French pastry cook of the head of state Charles-Maurice de Talleyrand-Périgord and at the head of the famous pastry house Bailly in Paris) improved the recipe. The Parisian pastry cook Antonin Carême (1784-1833) also perfectionated the choux pastry. The actual choux pastry is a legacy of Antonin Carême who was an apprentice of Jean Avice. Antonin Carême was renowned as “the King of the chefs and the chief of the Kings”.
Opéra is a French pastry composed of a succession of Joconde cakes (a beaten dough of cakes close to the génoise or the sponge cakes), a chocolate ganache and a coffee butter cream.
Religieuse (“nun” in French) is a pastry consisting in choux pastry and pastry cream, generally with chocolate or coffee. The preparation is similar to the eclair. It was invented around 1856 in the Parisian café Frascati by the Neapolitan glacier. But at this time, the pastry was different from today ; it was a square of choux pastry filled with pastry cream and topped by whipped cream. The origin of the name “Religieuse” is uncertain ; it may be because of the color of the icing sugar recalling the dresses of the nuns.
Sources : Wikipedia, http://palaisdeslys.over-blog.com/article-24472485.html, https://www.pourquois.com/francais/pourquoi-religieuse-patisserie.html and http://www.escoffier.org/le-guide-culinaire/glossaire/avice-jean/