I often hear "The Creek" used by pilot and ATC in the vicinity of Provo Municipal airport. I've been flying in this area for over 20 years, and I don't know what they are talking about. There are at least three rivers that empty into Utah lake in the vicinity of the airport, one of them is named "Hobble Creek", but it would seem presumptuous to assume that is the one that is meant.
I am interested to hear strategies for learning the locations of unpublished, but commonly used waypoints.