Can confirm this. Inconnu is indeed the french word for "Unknown", so one of the contributors who's using the French WoW vanilla client have had the "Unknown" name bug.
Some players can show up for you with the name Unknown if you log out during combat or if server crashed during combat and you did not restart your WoW client afterwards. There are other smaller things that can cause the Unknown name to occur aswell.
The name "Unknown" has been filtered out of realmplayers database, but both "Inconnu"(French) and "Unbekannt"(German) currently still show up. This has been reported for a future fix
