Protein names are funny things. Often they are chosen before much of the functionality of the protein is characterized, which means they are usually misleading. I wonder how much progress in biology has been retarded over the years by that simple fact.
The abbreviation Fto comes from "fused toes" mutation, but was also initially called Fatso because it is a relatively large protein (about 500 amino acids, nothing close to the huge ones like titin). Ironically, this name is quite important since it seems that Fto is very important in energy homeostasis in mammals. It is highly expressed in the arcuate nucleus. There is some correlation between Fto mutations and susceptibility to diabetes. Because of all that, the preferred descriptive name now is "fat mass- and obesity-associated gene".