In media science, the concept of the costume language is only vaguely defined. We propose a formal definition of this concept, which is based on the concept of pattern languages. In order to derive the patterns of such a language we introduce a method that supports capturing knowledge about clothes, identifying costumes based on clothes and abstracting costumes into costume patterns. Thus, costumes are understood as concrete solutions to the recurring problem of achieving effects in films by using clothes. Associations between patterns and concrete solutions are maintained to ease the development of concrete solutions from a patterns abstract solution description. Our method and its associated formalizations are generalized to support the identification of patterns from concrete solutions in other domains.