A pejorative can start out nice and then turn into one depending on how it's used and how the people who say and hear it understand it. "Princess" said sarcastically can mean someone high maintenance who acts superior to others. Here, I'll use a Japanese example:
Kisama(貴様) is a word often translated to be similar to "you bastard" or some equally rude way to say "you", but was originally a honorific "Originally used as a term of honor and respect in the correspondence of samurai households, used to refer to social superiors."
As for some of your other examples, I had a polish teacher. You selected "poles" as an example (I assume because of the similarity with shortening the word), but he told us Polack was a derogatory term we shouldn't use for him. This is a word some polish themselves will use, but is still derogatory.
Another example is "paki", which is also a shortened word, but originated in the UK as a slur for Pakistani immigrants. In racist style, they also extended it to people in similar regions as Pakistan, similar to how many racists would just call Asians "chinese".
Lots of terms become offensive over time. Even Oriental just meant eastern, in contrast to Occidental for Western. Negro comes from black, and an older and less racist set: sinister.
Sinister today is known as sneaky in an evil way, but it originally meant left handed. Dexter being the opposite, right handed. Yet dexterous today means good with hands while sinister just has the negative connotation.
For some reason on my client, it can't remove the spoiler (gives a network error). I'm assuming it says that since the ball has more mass, it has a higher attraction rate of its own gravity to Earth's, so does fall faster in a vacuum but so miniscule it would be hard to measure?