entomology from the greek ἔντομον for "insect", the tom actually is the same tom in atom.

- "The Greek word entomon, meaning “notched,” refers to the segmented body plan of the insect."

https://www.britannica.com/science/entomology

- "Etymology : From ἐν- (en-, “in”) +‎ τόμος (tómos, “slice”)."

https://en.wiktionary.org/wiki/ἔντομος#Ancient_Greek