For detailed information check this: https://en.wikipedia.org/wiki/Master_Password
Master Password is an algorithm designed by Maarten Billemont for creating unique passwords in a reproducible manner. You could also create unique (but reproduce able) user names as well. Such passwords / usernames not even have to be saved at all...
This would be a great addition to Enpass. E.g. Enpass could offer passwords or usernames based on this algorithm as an additional service...