Okay, this might be a long one. The subject is huge, even within the specific focus I am going to try to maintain for this post. Better get a cup of tea before we start.
During my schooldays, I learned the word 'pikey' as a colloquial adjective for miserly, niggardly. Its meaning emerged through contextual usage, with a particular emotional flavour. At some point during my teens I saw the word used as a noun, scrawled in graffiti near a gypsy encampment, and thereby learned to my surprise that it was a racial slur.
I don't have such a clear memory of the moment of revelation when I learned that the word 'cotton-picking', heard in cartoons in my childhood, likewise carried huge cultural baggage. But I can clearly remember the days of innocence when it was just sound, a mannerism used as an intensifier to give a certain rhythm and tone to the speech.