What is “Peach’s ???” in Super Mario RPG

Much to the surprise of fans everywhere, the mystery item called Peach's ??? was kept in the remake of Super Mario RPG. There are a lot of theories about what this item could be, but Nintendo has neither confirmed nor denied any of these possibilities. Here are some of the most common theories online.

1. Some Reddit users and old forum posts think that it is Peach's brassier. Since the Japanese version of Super Mario RPG has it listed as ピーチのXXX or Peach's XXX and the English version has three question marks, it must be covering up a three-letter word. Since Bra is a three-letter word in English and the Japanese word for Bra is taken from English, that could make sense. However, the item in other languages Super Mario RPG has been translated to don't match this rule, including Spanish, where the item is called "(?) de la princesa Peach."
2. Occasionally, you will see a theory that it is Peach's panties on the chair; this doesn't make much sense, considering that the rest of her room is spotless, and she has a maid to help keep it that way. There's no way an attendant in the house of Toadstool would leave undies out for Mario to find.
3. This hidden item could be an erotic novel or some sort of suggestive toy. If you interact with the item before Peach is at your party, the panicked attendant scolds you, bribing you with a mushroom item to return it. If you interact with it when Peach is at your party, she will say, "Mario! Stop peeking into other people's rooms!" Based on these two reactions and the location of the secret item, this seems like a pretty likely candidate for what Peach is hiding.