Device host name is retrieved from each device automatically, while the friendly name is assigned to it manually. The friendly names feature allows network administrators to assign custom names to devices, to aid device identification and be user-friendly (hence they are called 'friendly').
If a device has a friendly name, this means that you (or someone else using the same NetScanner) added it. In your case, it appears that the host name was copied to the friendly name, which is not really achieving anything.
A friendly name can be linked to IP addresses, MAC addresses, or host names. My best guess that in your case it was linked to the IP addresses. Some of the IPs have changed over time, and that's why you are now seeing the names that belong to a different device.
To add, remove and edit friendly names, simply go to menu Options - Friendly Names / Comments...