Just noticing:

Gamma is the third letter of the Greek alphabet.

Zimmy's real name, Zeta, is also a letter in the Greek alphabet, the sixth (don't know that the number matters but just thought I'd include the details).

Omega is often used to symbolize the end because it is the last letter of the Greek alphabet.

Don't know what it means, but Zimmy went from calling one name, Gamma, to saying the other as if she recognized it. It may be that she's just aware of what Loup said. But, maybe Omega is something alive (or close to it) that Zimmy, being Zimmy is aware of.