Normally used in conjunction with GFY (Go Fuck Yourself). Corporations frown upon their employees sending curse words in the body of their emails. Sometimes, though, someone will just piss you off so badly that you have to respond. In that case, you will tell them to GFY and GHY
Hey, Greg, regarding your last email, GFY and GHY. Thanks. Tammy
Go hang yourself.
Pompous Idiot: "Legalize it! Weed never killed no one!"
Rational Human Being: "ghy"