In Greek antiquity, a cone-shaped projection of the upper part of the tragic mask which was supposed to give it size and impressiveness.(noun)
The Century Dictionary (Public Domain)
Use "onkos" in a sentence
"But if one looks back even further behind the Greek to the ancestral Indo-European language, the etymology of the word onkos changes."
"And that's another Hippocratic term onkos, is a Greek word, and it simply means masses."
"Another Greek word would intersect with the history of cancer—onkos, a word used occasionally to describe tumors, from which the discipline of oncology would take its modern name."