Name Check

 Yeah, what is in a name?  Full Name, Default Name, Display Name, Username, Modern and Legacy... 
Originally when you joined Second Life, you chose a first name - it could be anything you wanted that wasn't wasn't too obviously rude or copyright infringing. Then you picked a last name from a list of about 50 possibles. This surname list was gradually refreshed, so that people who joined around the same time would often find they had 'cousins' - think of the improbable art trio of Selavy, Bryn and Saveme Oh, all linked by that surname, if not much else.  

It was a golden age of witty and punny creativeness, and a huge dose of crass daftness also. Many of the Last Names invited a play on words, and people rose to the challenge with great choices like AM Radio, Hok Wakawaka, or Rolling Shuffle. I bet you can remember a few good ones, put them in the Comments if you want. 

It's painless and quick to change display names in SL

So far in Second Life's impressive 20 year lifespan, there have been over 11,300 Last Names (here's a list of them). That includes both the ones suggested by the Lindens, and custom names people have requested. Some of the earliest Last Names were Baskerville, Prudhomme, Jetaime, Sideways, and Binder. Interestingly in the first four years of SL, only 360 different Last Names were available, each being retired after a few days or weeks, apparently at whim.
Back in 2010 some big name changes happened in Second Life. New account holders had to pick just one name, and whenever legacy form-filling required a second name, they all used the same one - 'Resident'.