Cyclical variations in moods and energy levels have been recorded at least as far back as several thousand years. The words "melancholia" (an old word for depression) and "mania" have their etymologies in Ancient Greek. The word melancholia is derived from melas/μελας, meaning "black", and chole/χολη, meaning "bile" or "gall", indicative of the term’s origins in pre-Hippocratic humoral theories. Within the humoral theories, mania was viewed as arising from an excess of yellow bile, or a mixture of black and yellow bile.