While this
literally expands to "tah tah for now, okay, thanks, goodbye..." the pop culture connotation is that you are making a flippant or perhaps merely hasty retreat from a conversation with the
speed of a 1980s or 1990s
Anime school girl. The character of Yukio in Deadpool
2 comes to
mind, as well.
One can also shorten it further as "ttfn kthx bai" or "ttfnkthxbai".
Certainly related to, though a nuance in use of the constituant parts "ttfn" "kthx" and "bai". The "ttfn" adds a friendly aspect, while the "kthx" adds
snark, followed by the finality of "bai" - when combined it forms a powerful and ambiguous immediate ending to a conversation, though ironically is often not the last words. It's quite common to have the other party respond with expressions of either offense or solidarity with your assertion using this phrasing.
Friend: "So yeah, I know I've been telling
like every gory detail but ..."
doorbell rings
You: "OMG, my
pizza is here! I've got to
go, sorry!"
Friend: "No problem..."
You: "ttfn kthx bai"
Friend: "Bai"