"encysted tumor," 1706, medical Latin, from Greek atheroma, from athere "groats, porridge" (related to ather "chaff"), in reference to the matter inside; a word of unknown origin. For ending, see -oma. Related: Athermatous (1670s).
"a hardening," especially "morbid hardening of the tissue," late 14c., from Medieval Latin sclerosis "a hardness, hard tumor," from Greek sklērosis "hardening," from sklēros "hard" (see sclero-). Figurative use, "excessive resistance to change," is by 1954.
<a href="https://www.etymonline.com/word/atherosclerosis">Etymology of atherosclerosis by etymonline</a>
Harper, D. (n.d.). Etymology of atherosclerosis. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/atherosclerosis