Academism was a dominant style in European sculpture and painting in the eighteenth and nineteenth centuries. It was called so because it was dictated by the French Academy of Art, Académie des Beaux-Arts, which was probably the most influential art school back then. If somebody wanted to make a career, they needed to follow a few simple rules: excellent disegno (drawing), realistic colours and … lots of naked bodies on canvas!
It was a joke, but there was a grain of truth in it. Young students of the Academy had to study anatomy of classical sculptures (mostly naked) and live models (yes, naked) in order to master their drawing skills. And since Neoclassicism was in high fashion in the Academy and history paintings were at the top of the hierarchy of genres, naked bodies were virtually everywhere.