Wi-Fi Device Name

Settings:- Click More which is under Data Usage: - Tethering and Mobile Hotspot:- Setup WiFi hotspot:- Change Network name = Job Done

Hope this helps
 
That seems to change the SSID,
i.e. the name of the tethering network using the device as an access point, rather than the hostname of the device on any other network. This is not about tethering.