Most three-character strings are inert. They’re blank, which is useful, but they bring nothing with them. This one arrives with a meaning already attached and costs the buyer nothing to inherit it. B4N has meant “bye for now” since the earliest days of text messaging and chat. It’s in the abbreviation dictionaries, it predates the smartphone, and a substantial number of people read it without pausing. That warm conversational sense suits messaging, social, travel, or anything with a farewell in its user flow, which is a more common moment in product design than it first appears.