The popup isn't from an icon, it is from an app. You then need to find and remove the app that is doing it.
It could be any app you personally installed or updated. It could even be one you didn't install, but that another app you did install or update installed it on the phone without your permission. Happens more than you might think.
So start with the apps you recently installed and updated. Uninstall those apps and/or updates then restart (power off and back on) the phone and see if this resolves the issue.
Should it continue, then you will need to look through your apps (go into "Settings" and then "Apps") and search for ones you see were installed and you don't recognize. Before uninstalling any you find be sure you search online to find out if they are something you should remove.
Should none of this work, then you are look at either a virus or malware, which you would have to clear from the phone, or do a complete "Hard Reset" of the phone to remove everything and start from scratch.