I have an unknown device showing on my surfboard app.   I've been throughout my home and can't find any other devices I haven't named in my surfboard. 

I want to remove or block access to this device but I don't know how to do either of those things on my android phone app.  Can you please tell me how I'd go about blocking or deleting this device from my system?

I have my 2 printers

My NEST  Thermostat

Son's Play Station

Firestick

VIZIO TV and all other things that were connected to network on it

ROKU TV

3 EVO FORCE1 boxes for televisions

My phone

Son's phone

Son's laptop

My laptop

Been through the house, no idea what this last thing could be.   Unplugged Alexa,  but apparently that is Bluetooth.