The story
From pie crust + lease, in reference to the lease only including the topmost layer of the land. Coined due to the fact that estates in land include the subsurface by default.
Etymology from Wiktionary, CC BY-SA 4.0.
pie crust lease
Today it means: A lease for the surface of some land or structure (such as a bridge), which excludes the subsurface or land beneath. Full definition →