The Greek kaetos and Latin balaena, though sometimes, especially in later classical writers, specifically applied to true cetaceans, were generally much more comprehensive in their signification than the modern word whale.
"The Earth as Modified by Human Action"
George P. Marsh
The sternum of the balaena consists of a broad, flattened, heart-shaped or oval presternum.
"Natural History of the Mammalia of India and Ceylon"
Robert A. Sterndale