The term 'BACK FIN' is a combination of two words, 'BACK' and 'FIN'. The first word, 'BACK', refers to the rear part of an animal or object. The second word, 'FIN', is a flat appendage found on the BACK of some aquatic animals, such as fish, which helps them to move through the water. Together, these two words form the term 'BACK FIN', which is also known as a 'DORSAL FIN'. A DORSAL FIN is a FIN located on the BACK of an aquatic animal, usually near the tail, which helps the animal to swim and maneuver in the water.