Star Trek: 10 Crazy Facts About Ferengi
7. Gold-Pressed Latinum
The focus of Star Trek has always been the Federation and Starfleet. Humanity had left a lot of things behind over the centuries, including the need for currency within its own society. This wasn't true for many other species and governments who still used a monetary system, frequently based on Latinum.
A rare liquid metal that had a silver-ish color, Latinum was incredibly valuable. Gold wasn't, so it was used to create a means of containing the Latinum for easy transactions. This is how, and why, Gold-Pressed Latinum was developed.
While it's used by a number of species as currency, it has an what's best described as a mythical status in Ferengi culture. Almost everything they do is based on Gold-Pressed Latinum, and accumulating it. Several of the Rules of Acquisition are either focused directly on Gold-Pressed Latinum or reference it in some fashion.
Even Nog, the first Ferengi to join Starfleet, still had an ingrained love for Gold-Pressed Latinum. It's hard-wired into Ferengi culture.