Gotten is the past participle of to get in both standard American English and Scottish English (I won't say Scots because that is often regarded as almost a separate language from English). I wouldn't say it myself but then it isn't part of my south western English (North Wiltshire) dialect, my wife on the other hand used it all the time (she was from Orkney).

Perhaps it's a sly hint to the fact that you can go online to learn the meaning of words you don't recognize:

https://www.google.com/search?q=define+gotten

What's wrong with "gotten"?

To me (British English native) it sounds like a non-word. I'm well aware of its meaning and that many "Americanisms" are actually old English usage. It still sounds to me like something a cartoon weasel would say.