The answer to the crossword is EPEE, which stands for Épee de L'Abbe de l'Épee, the name of the French priest who invented a sign language in the 18th century. The Abbe de l'Épee was a teacher of the deaf and developed a system of communication that used hand gestures and facial expressions to communicate with his students. His invention of a sign language revolutionized the way deaf people communicated and is still used today.