It is the name of the device. This is how entity ids (and names) are generated when you add a device now. domain.<device_name>_<sensor_name>
It is stupid and unneeded but this is how all other integrations work so ESPHome has to fall in line too. 
There are mitigations planned for the ESPHome Builder config but they are not released yet.
There’s another topic here: HA 2025.5 ESPHome device names now on frontend
You can manually edit the names and entity_ids in Home Assistant. Be thankful it is only one device. This has affected people with thousands of names to change.