Well, the answer is books.
They could be scanned wrong, from other languages, or even an author wrote them wrong.
I suggest you read Recaptcha's about page.
To archive human knowledge and to make information more accessible to the world, multiple projects are currently digitizing physical books that were written before the computer age. The book pages are being photographically scanned, and then transformed into text using "Optical Character Recognition" (OCR). The transformation into text is useful because scanning a book produces images, which are difficult to store on small devices, expensive to download, and cannot be searched. The problem is that OCR is not perfect.
reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.
As I said, error in OCR -
I believe that Indelms is meant to be Indians - located from United States Statutes at Large Volume 40 Part 2
polietry - most likely scanned wrong from Popliteal - a medical term.