If your user name appeared to be a real first and last name (fictitious or not), your user name has been changed to just your first name. As of May 1, 2018 no full real names are allowed as user names.
Which all sheds an interesting light on the old quote by Ruskin:
"Great nations write their autobiographies in three manuscripts—the book of their deeds, the book of their words, and the book of their art. Not one of these books can be understood unless we read the two others; but of the three, the only quite trustworthy one is the last. "
- John Ruskin (1819 - 1900)