Phlegma

...Inflammation is a general term for diseases that include the word "flame," as well as diseases that do not include the word "flame" but are accompanied by fever, pain, and swelling, such as the common "swellings" and "growths" that we see in everyday life.It is a medical term that indicates a different group of diseases from tumors, circulatory disorders, and deformities.
[History of inflammation research]
The concept of inflammation has been used since ancient Greek medicine as the word bregma (cellulitis, for example, a condition in which a "blood boil" spreads widely through the subcutaneous tissue), which indicates the concept of "burning." In other words, inflammation was a "disease that burns like a flame," or a "disease accompanied by fever."

*Some of the terminology explanations that mention "phlegma" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…炎症とは，このように〈炎〉の付く病気や，また〈炎〉の付かない病気でも日常よくみる“はれもの”とか“できもの”のように熱，痛み，はれを伴う病気の総称であり，腫瘍とか循環障害とか奇形などとは異なった疾患群を示す医学用語である。
［炎症の研究史］
　炎症の概念はギリシア医学の昔からプレグマphlegma(蜂巣炎，たとえば“できもの”が皮下組織に幅広く広がった状態)の言葉として使われており，この言葉は“燃える”という概念を示していた。つまり炎症とは〈炎のように燃えている病気〉，すなわち〈熱を伴う疾病〉ということであった。…

※「phlegma」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報