I earned certification in the early days. “Scrum Master” was supposed to be a team member who took on the role of interacting with external stakeholders, and help the team organize the work.

The scrum master protects the team from interruptions and un-scheduled work and facilitates planning meetings.

More recent iterations minimized the Scrum Master as a first class role. Scrum Manager sounds like a new role the process.

I did a search, came up with this gem.

All the other search results did not have “scrum manager”, and the end of the video indicates this is not an official role in Scrum, but a term used for managers who are all in on the values of the scrum process.