Cancer anorexia-cachexia syndrome (CACS) is a lethal but poorly defined involuntary wasting disorder. Loss of skeletal muscle and fat distinguishes it from starvation. Cachexia has been described as a clinical syndrome since ancient times, and the poor prognosis has long been acknowledged. In this article we have reviewed historical perspectives on cancer cachexia, and commented on modern definitions. In cancer cachexia, most historical descriptions included anorexia, wasting and a pale complexion. Other associated symptoms, such as fatigue, early satiety and taste changes, were inconsistently described. Newer descriptions have not significantly expanded the clinical picture. Today, there is still no consensus definition, hindering research on early diagnosis and effective therapy. The language descriptors used to characterise the syndrome are important. For example, the word ‘cachexia’ itself may mislead; perhaps cancer-related wasting syndrome is more accurate. Cancer anorexia-cachexia syndrome is a disorder associated with high morbidity and mortality, and deserves greater attention in both clinical and translational research.