Different words for different reasons. "C*nt" was originally a word with a strong feminist history, so with that one it's easy to see why/how it was turned into a slur. "Sh!t" probably became taboo around the time that class separation made certain people far less likely to be in its presence constantly. "Goddamn" was almost certainly taboo-inated due to the church considering it blasphemous to use the word "god" in everyday language, except in a positive-propaganda way... and so on. They're probably more interesting when studied individually.

Attitudes changed. Political correctness has, for example, made the "f-word" (and it doesn't directly relate to fornication *LOL*) an offense for which rehab is the only remedy.

I think there are several reasons. A word can be considered impolite in mixed company (going back many, many years) usually becasue it's more crass than euphamistic and so it becomes undesirable to utter for fear of being considered low-class or without class. A word can take on a pohibitive nature if it is seen to curse a diety. To say G**D**** is to use God's name to curse something, which is in direct violation of one of the Ten Commandments. Hence, it is taboo. There are certain words, too, that were created or adopted with the specific intent of conveying bias or denegration toward another person. Racial slurs and epithets would fall under this category. The better part of society understands there is no place for the vile and malicious description of individuals, and so the words become taboo.

The taboo is a social phenomenon; some terms are therefore regarded as taboo by some people, but not, by others. Let us take the weasel as a case in point. We have a lovely animal in principle, but a farmer may think otherwise because if it eats his chicks and his hen's eggs, he will scream blue murder by the sole fact of hearing its name. Extremely religious people find it impure to speak about things in which blood is involved: labour (birth), menstruation, etc. Euphemisms can even make the harsh reality appear natural, which is why they are used by politicians in order to take the people in and endear themselves to the public: neutralise (= kill, murder). It is not the same to say: The natives have been neutralised as to say: The natives have been exterminated / massacred / killed. The reality is the same, but not the way to express it, and the effect that it produces. Dysphemisms consist in employing disparaging or negative terms to describe people, things, facts, etc. We make use of them to deride the person, thing or fact referred to and there may be a humorous tone: poetaster, old banger (to talk about a luxury car), and so on and so forth. They can also be cruel: Last night that thing (= my mother's boy friend) came home to have dinner. http://www.polseguera.com/colaboracion/english/6en.htm A taboo is a socially enforced prohibition, and in language such a prohibition forces the substitution of another word for one that is taboo. Sometimes taboos in language are inexplicable, but others can be traced to specific social attitudes. Generally only when manners have changed do old taboos seem silly and fall away; some Renaissance English might seem pretty explicit today, even to many liberated modern American ears. Some taboos enforced by Standard English at least in mixed company and in most publications earlier in the twentieth century have eased radically since the late 1960s, especially for those vulgar or obscene words involving sexual intercourse and excretion; many have much wider currency, if not full acceptance, in both speech and writing, than could have been envisioned forty or fifty years ago. On the other hand the taboo against words of racial and ethnic opprobrium that Standard English enforced only moderately and selectively earlier in the century is now much more rigorously enforced in both speech and writing and among nearly all users of both Standard and Common English. http://www.bartleby.com/68/19/5919.html http://nmc.itc.virginia.edu/E-folio/1/EDIS542/2003Fall-1/cs/UserItems/Pages/sc6bj_873.html We’ve learned about taboo word theory. We’ve explored its categories, its power and its flexibility. We’ve experimented with its creative side in our poetry and even glimpsed how students use it communicate by writing graffiti on study carrels. Now we want to understand how taboo words have really developed. We want to pass on this historical development to our students so they can see that words, even taboo words, are just as alive as any other organism. Word history is quite a fascinating subject but we do not feel that it is necessary to go on a long detailed journey within this project. Instead, we focus on a brief social history of how "dirty words" have been viewed in the English language over the past thousand years, starting with Anglo-Saxon views on taboo words, moving through the Norman Conquest and the Medieval Ages right up to the twentieth century. http://nmc.itc.virginia.edu/E-folio/1/EDIS542/2003Fall-1/cs/UserItems/Pages/sc6bj_752.html

People just wanted to find a way to put others down and make them feel unacceptable.

Taboo words are very cultural. They pertain to the culture and epoch. eg in the middle ages in England, the word "guts" was quite offensive, but not now. On the other hand some words which were acceptable in the Middle AGes, "shiten" was a normal verb, but is now considered crude. It depends on what a culture considers worthy of general discussion, and what is considered personal or shameful.

probably cause people didnt like them

The emotional charge behind them and the interpretation being generalized with that charge. when I was a kid I didn't understand why such strong reactions to certain words which to me were only words. Add context and interpretation and you've got a firecracker.