@cginva 

FYI

Azurewave are Wi-Fi NIC device manufacturer in Tiawan. These devices are used in any number of computing and IOT devices. So it may have even been something as innocuous as a Google Streaming device or your neighbor's notebook computer. 

But yes as you found out by changing your password, you neighbor had to have had your Wi-Fi password to connect to your Wi-Fi ! 

Good thing you changed the password.  

And as TP-Link stated,  please ensure your Wi-Fi password is very complex and not easily guessed.

@DAServices After I changed my password the Azurewave device reappeared.  I blacklisted it and it has not come back as of now.  I had something similar happen once with my Brother printer.  An unknown device popped up that turned out to be the internet connectivity module of that printer.  But this time I have not added any new devices to my network in months and then all of a sudden this Azurewave device pops up.  I read that Azurewave is used in certain IoT devices.  I have a smart doorbell and a smart garage door opener.  But both of those devices have been on my network for over a year with no sign of Azurewave until now.  Is it possible that one of these device manufacturers did some sort of update that caused the Azurewave issue?  
 

There's no way someone would have known my new password so quickly after I changed it.  I suspect this is somehow related to a device already on my network that uses Azurewave technology, but do not understand how it would go unseen for so long.

@cginva 

Same here. Noticed that new device joined the network.

Hon Hai Precision Ind

Blocked it for good measure.  Checked the MAC, and it turned out to be my PS4.

For some reason, the DECO sees the manifacturer of the equiptment and not the name (?)

So, it would help remembering if anything new was connected to the wifi and then check the MAC (older devices cant change this, unlike new ones that can randomize)