"Ferengi" and similar terms are Arabic names for European traders, or for Westerners in general. The name is likely derived from the Arabic word faranj or ifranj, or Persian farangi, meaning "Franks". In Ethiopia, ferenj or ferenji has the same meaning, as does farang in Thai. The source of the name is likely from the Byzantine Greeks who were the Westerners' neighbors; this usage spread to the Near East, Asia, Africa and even China.[3] Greeks still sometimes use fra[n]gkoi (φράγκο? as an exonym for Western Europeans, and the modern Greek term ferengios (φερέγγυος, ο φέρων- εγγύηση, ο δυνάμενος να εγγυηθε? literally translates as "the able to ["bear" (=carry)] guarantee (himself)", the trust-worthy, and not only in a financial way! The term was used as a partially derogatory term in India to denote the British.
http://en.wikipedia.org/wiki/Ferengi#Etymology