Hello,
it looks like a bug: entername is there as lang string but not actually used in the code, https://github.com/moodle/moodle/blob/7d659f21679fcabbc6c232a510e38ef2eb299d67/lib/editor/atto/plugins/media/yui/build/moodle-atto_media-button/moodle-atto_media-button.js#L156.
If you raise an issue in the Tracker and post here its id I'll follow it and propose a patch.
TIA,
Matteo