Atlas is a code-name that has popped up in a few Chromebook-related leaks over the past few months. It is linked to development by Google and has been thrown around as a Pixelbook successor. Now, 9to5Google's sources claim that it is indeed part of this series, but not perhaps as some may have assumed.
https://www.notebookcheck.net/Google-s-Atlas-may-be-named-the-Pixelbook-Go-at-its-launch.435504.0.html