Where does “Teleostei” come from?

Teleostei (Translingual) comes from Ancient Greek τέλεος, from Ancient Greek τέλος, from Ancient Greek μέρος, from Proto-Hellenic *(h)méros.

Ancestry of “Teleostei”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	τέλεος	genitive singular of τέλος; complete
2	Ancient Greek	τέλος	completion, accomplishment, fulfillment,...
3	Ancient Greek	μέρος	part, component, region; share, portion; one's...
4	Proto-Hellenic	*(h)méros	—