This study aims to explain the formation and factors of vulgar language. Vulgar language implies underestimative and contemptuous expressions. Some scholars divided these expressions into vulgar language and informal item or slang. But I determined that vulgar language means [+contemptuous] and [+estimative] feature`s expressions. Vulgar language consists of words, expressions, and meanings that are informal. I focused on the formation and factors of vulgar words. These words are formed by linguistic factors or social elements. I divided the main linguistic factors into three types: First, the fundamental contemptuous words that the words imply low value features, second the opposition words that these features gained by opposing estimates, and third are the figurative or unsuitable words. Sociogenic vulgar words are formed by the change of social structure or group consciousness. But these words gained underestimative and contemptuous feature through opposing relations. For example the Korean word ``GYEOJIP(겨집)`` means wife or women. This word is abusive or a swear word opposite ``ANEA(안히>아내)`` or ``YEOJA(여자)``. These opposing relations are formed by social change.