Hannah Keyser at mental_floss suggests five ways Grimms’ Fairy Tales changed after the first edition. Of particular interest to me (naturally) was how faeries in the first edition got recast:
In the first edition, the harbingers of magic were almost always fairies—unsurprising in the Fairytale genre. But during the time that the Grimms worked, the Napoleonic wars saw French occupation of much of German-speaking Europe. Somewhere along the line, they decided to stop using the French term “fairy”—or sometimes “faerie”—and instead replace each instance with some other vaguely mystical being. For example, in Rapunzal the fairy became a sorceress, and in Briar Rose, better known as Sleeping Beauty, the fairies are changed into wise women.
My guess is the brothers Grimm got a nasty visit from something that told them the word “faery” isn’t exactly PC.