In texting, "XZ" is a Russian internet slang term that roughly translates to "I don't know."
While "XZ" might not be immediately recognizable in standard English texting abbreviations, it's a transliteration of the Russian phrase "хз" (pronounced roughly as "huz"). This phrase is a shortened version of "Хрен знает" (Khren znayet), which literally means "Horseradish knows," but is used idiomatically to express uncertainty or a lack of knowledge.
Therefore, if you see "XZ" in a text message, especially if the sender might have some connection to Russian language or internet culture, they are most likely communicating that they don't know the answer to your question or are unsure about something.
