A mispelling of a the term "Bah Fungoo" apparently, wich is an term invented by Americans for a slang/dialect form of the Italian "Vaffanculo".
Bah Fungoo is in no way how it's said or spelled.
-What was that italian expression to tell you to fuck off?
-Bah Fungu? Bah Fungoo!
-Nah, neither, that's not italian at all.
A Shackteau is a humble, weather-beaten, structurally questionable shelter located in a spectacular or highly coveted place—Wales, Jackson Hole, Sun Valley, Crested Butte, coastal Maine, the Alps—where the building itself may be worth almost nothing, but the dirt, view, access, and mythology make it absurdly valuable.
In use:
Shackteâu - We thought it was an abandoned shed until the realtor called it a rare alpine Shackteâu with unobstructed views and listed it for $2 million.