The term epidemic derives from a word form attributed to Homer's "Odyssey", which later took its medical meaning from the "," a treatise by Hippocrates. Before Hippocrates, , , , and other variants had meanings similar to the current definitions of "indigenous" or "endemic". Thucydides' description of the Plague of Athens is considered one of the earliest accounts of a disease epidemic. By the early 17th century, the terms endemic and epidemic referred to contrasting conditions of population-level disease, with the endemic condition at low rates of occurrence and the epidemic condition widespread. The term "epidemic" has become emotionally charged.