Why do we can the meaning of word to mean something else?

Question

Like for example most cuss words are translated to something bad (since there are children on this site I will refer to them by there first letter)

a word means donkey but we use it to say butt.
b word means female dog we use it call some one a controlling, crazy, or annoying person or to try and compliment someon.
hoe means garden tool but we changed it to mean a woman who goes out with handfuls of men.
gay means happy but we use it as homo

Why do we change the meaning of words?

Answer 1

For the same reason that schoolkids adapt the words and refer to a 'bick' or they replace the f in the f-word with another letter or sound (smuck, puck, etc).

It's just adapting language to get away with saying something.

Answer 2

The 'B' word references a female dog whose purpose is to give birth, only. So, you could see how a word like that might be offensive to a woman. 'Hoe' is short for another word that starts with a 'W'.

"Why do we change the meaning of words?"

Language and words evolve all the time, and just like evolution it is seemingly random. It may be strange, but the purpose of words is to facilitate communication, so if we can understand it, it works.