I just asked someone whose user name was basically a bunch of gibberish with a couple of periods breaking it into three parts how he got the name (registered in November 2013). His answer was "they kind of just gave it to me". The first part was a nonsense word that maybe he picked, the second part was the first two letters of his last name (coincidence?) and the last part was a random string of letters. I guess ebay was, at least for a while, generating nonsense usernames.