I would guess Wordle picks from a big bag'o'words. The words are all fairly common - "regel" is not going to show up - but I see no evidence the list favors "zebra" over "taint" (which has occurred, BTW).

The original Wordle had a hard-coded ordering that was visible in the source. I had a toy around with the list (as did many other people) a few years back, you can see my copy of the word list here: https://github.com/andrewaylett/wordle/blob/main/src/words.r...