Definition of TTFN in English:

TTFN

informal
  • Ta-ta for now:

    ‘anyway, TTFN, and hopefully I'll have plenty of time to write when I get back’
    • ‘In fact a month ago my plan was to close up shop at the one year mark, say TTFN, and delete my account.’
    • ‘They also rely on those annoying acronyms that hard-core E-mailers have thrown around for years: BTW (by the way), LOL (laughing out loud), TTFN (ta-ta for now).’
    • ‘TTFN, we are off out to have a pub lunch.’
    • ‘His jocular banter delivered through mutinous teeth has me reaching for the off-switch quicker than you can say TTFN (ta-ta for now - aaargh!)’

Origin

1940s: popularized by its use as a catchphrase in the 1940s BBC radio programme "ITMA".