XO has long been written shorthand for hugs and kisses in letters, cards and later in texts and social posts, where it closes a message with affection. As chats moved into video, creators began turning familiar written sign-offs into tiny audio cues, and this sub-second version fits that habit. It circulates on soundboards as a shareable reaction rather than a clip from a known film or song, passed between editors who need a quick, friendly closer that audiences understand without any setup or explanation needed.