No one is really giving you the literal reason why some words are bad and others arent.
Many, many centuries ago, England was made up of about 20 different warring kingdoms. One of these kingdoms called on the help of some Germanic tribes on mainland Europe to help defeat a rival kingdom, since the people occupying England couldn't fight as well as the Germanics who sacked Rome. The Germanics saw that England was a ripe country for living and after attacking one kingdom and seeing how much of a fighting advantage they had, Germanic tribes (norman french, to be precise) took over almost all of the contiguous England (the only one who offered any real resistance was Artorius in Northwest England).
So now that the Norman French Germanic tribes have sacked all the royal families in England and assumed control of the political systems and communities, they are left with the peasants who they had no need to destroy, because they are peasants and posed no threat. However, the Norman French speaking new upper class speaks a completely different language than the gutteral English that the peasants spoke.
Specific language differences include the reason why in modern english, we distinguish the food from the animal, whereas in almost all other languages this does not happen. For example, cow in the field is called cow, but on the table it is called "beef", which is a french word. When the new upper class demanded, LE BEEF, the peasants understood that they had to go kill the animal that they call the cow in the field and cook it for their masters. Upon setting it on the table, the french could exclaim, AH! LE BEEF! You get the picture? Same works with chicken being poultry on the dinner table, ect.
Also, this leads to swear words. Eff you see kay simply meant to fornicate, it had the same (and still does) meaning as intercourse. However, it was considered unruly and low class to use such peasant words and so instead we have the upper class french word Intercourse.
Overall, this invasion of england created the version of english we use today. Most words over 2 syllables long come from norman french, like fornicate or intercourse or even all the political terms in todays society like barister, ect. However, the words we use most per day (about 1000 of them) mostly come from the Old english that the peasants spoke.
Now go tell all your friends my story.
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