Unknown wifi connection in my Connection dropdown menu
This is quite likely (no guarantee) that there is someone nearby with a WiFi device (Phone, printer, WiFi 4G router, etc) that generates a different name each time it turns on.

Note that the signal strength is pretty low. so it is not likely all that nearby. Using a WiFi stumbler might give you more information about the device as most WiFi devices will often self-identify with a Manufacturers name or model number. The stumbler software could also potentially help you locate at least which direction the WiFi source is.

Is it possible that someone is nearby trying to hack into your systems? Yeah. Is it likely? No, unless you have a lot of money or have access to valuable information or goods, or a person of interest to someone gathering intelligence on you it is unlikely you are a persistent target of attack.