American Heritage Dictionary
Profanity by definition is those "bad words".
PRONUNCIATION: pr-fn-t, pr-
NOUN: Inflected forms: pl. proÃƒâ€šÃ‚Â·fanÃƒâ€šÃ‚Â·iÃƒâ€šÃ‚Â·ties
1. The condition or quality of being profane. 2a. Abusive, vulgar, or irreverent language. b. The use of such language.
ADJECTIVE: 1. Crudely indecent. 2a. Deficient in taste, delicacy, or refinement. b. Marked by a lack of good breeding; boorish. See synonyms at common. c. Offensively excessive in self-display or expenditure; ostentatious: the huge vulgar houses and cars of the newly rich. 3. Spoken by or expressed in language spoken by the common people; vernacular: the technical and vulgar names for an animal species. 4. Of or associated with the great masses of people; common.
ETYMOLOGY: Middle English, from Latin vulgris, from vulgus, the common people.
OTHER FORMS: vulgarÃƒâ€šÃ‚Â·ly —ADVERB
WORD HISTORY: The word vulgar now brings to mind off-color jokes and offensive epithets, but it once had more neutral meanings. Vulgar is an example of pejoration, the process by which a word develops negative meanings over time. The ancestor of vulgar, the Latin word vulgris (from vulgus, “the common people”), meant “of or belonging to the common people, everyday,” as well as “belonging to or associated with the lower orders.” Vulgris also meant “ordinary,” “common (of vocabulary, for example),” and “shared by all.” An extension of this meaning was “sexually promiscuous,” a sense that could have led to the English sense of “indecent.” Our word, first recorded in a work composed in 1391, entered English during the Middle English period, and in Middle English and later English we find not only the senses of the Latin word mentioned above but also related senses. What is common may be seen as debased, and in the 17th century we begin to find instances of vulgar that make explicit what had been implicit. Vulgar then came to mean “deficient in taste, delicacy, or refinement.” From such uses vulgar has continued to go downhill, and at present “crudely indecent” is among the commonest senses of the word.