I found an old string into
locales_source table, like that:
8.5.3 version seems outdated.
I would like to understand the usefulness of the keep this data in my database ? How to clean it properly ?
In Drupal 7, you could delete unnecessary strings in the UI.
Drupal 8 and 9 are missing this functionality; there is an open bug report to add it back, and hopefully it will eventually be fixed in Drupal 10.
There is a working patch in the issue to get a mostly working version of the function now.