Fur is used in reference to the hair of animals, usually mammals, particularly those with extensive body hair coverage. The term "pelage" (French, from Middle French, from poil hair, from Old French peilss, from Latin pilus; first known use in English circa 1828.) is sometimes used to refer to the body hair of an animal as a complete coat. Fur is also used to refer to animal pelts which have been processed into leather with the hair still attached. The words fur or furry are also used, more casually, to refer to hair-like growths or formations, particularly when the subject being referred to exhibits a dense coat of fine, soft "hairs." Animal fur, if layered, rather than grown as a single coat, may consist of short down hairs, long guard hairs, and, in some cases, medium awn hairs. Mammals with reduced amounts of fur are often called "naked", such as naked mole-rat and naked dogs. An animal with commercially valuable fur is known within the fur industry as a furbearer. The use of fur as clothing and/or decoration is considered controversial by some people: most animal welfare advocates object to the trapping and killing of wildlife, and to the confinement and killing of animals on fur farms. Fur has been a major challenge for 3D computer graphics artists due to its visual complexity and physical properties. The first movie which made extensive use of CGI fur was Pixar's 2001 film Monsters, Inc.