It's a saying in which you say out of sheer fustration instead of actually swearing.
What you tell people what it means may vary but commonly used as That's not nice.
However what your really saying is Fuck You And The Horse You Rode On.
In a professional setting or a place with parents and their children. Instead of embarassing yourself by cussing like an idiot. Simply in a calmly matter say Fuathryo. To them, It may be another language.
After being told by my best friend that he cheated with my girlfriend; Realizing my daughter was in the room, I told him fuathryo and left.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.