Injury that’s so embarrassing no one is allowed to mention it?

The answer to this crossword question is TABOOBOOBOO. This is a play on words, combining the words “taboo” and “boo-boo”. A taboo is something that is forbidden or not allowed to be mentioned, while a boo-boo is a minor injury or mistake. Therefore, a “taboo boo-boo” would be an embarrassing injury that is not allowed to be talked about. The repetition of “boo” in the answer adds a playful tone to the phrase.