word-forming element meaning "surgical removal," from Latinized form of Greek -ektomia "a cutting out of," from ektemnein "to cut out," from ek "out" (see ex-) + temnein "to cut" (from PIE root *tem- "to cut").
<a href="https://www.etymonline.com/word/thoracotomy">Etymology of thoracotomy by etymonline</a>
Harper, D. (n.d.). Etymology of thoracotomy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/thoracotomy