One Day Mafatu: Soon; eventually; Used to declare your intentions are on track, and will happen…just not today.
A promise of future vengeance for a real or perceived wrong;
(I’m not too sure of the origins, but Mafatu was the main character from Armstrong Sperry’s growing up novel, The Boy Who Was Afraid.)
I know I should be saving my money but… I will. One day mafatu.
Yeah you wait there boy – one day I gonna smack your face properly saraga. One day Mafatu…
#1 by wendy on October 29, 2009 - 11:22 am
Hey, that is a very old book! I was teaching that in English way back in the 60s – perhaps at Penang Sangam High School. Is the book still being taught in Fiji?
w.
#2 by Wilson on October 29, 2009 - 11:46 pm
Yep – loved that book
Hmmm don’t know if its still in the curriculum – i dont think so though 
#3 by Kania Tiko on November 5, 2009 - 4:06 pm
I think your definition is wrong, isn’t it really about a promise of future vengeance for a real or perceived wrong?
#4 by Wilson on November 19, 2009 - 12:54 am
Hmmm good point. While I’ve never really used it that way, I have heard it like that. I guess it could come down to a promise that for sure, something’s going to go down in the near future. Slangs are kinda subjective
I’ve added your version in the post.
#5 by vitisurfer on April 23, 2010 - 1:55 pm
I’ve used this one allot. its more like ‘one day you’ll have to face the music’ or however they say that one. This meaning is used by the teachers which is more in line with the story.
its because Mafatu almost died in the ocean as a child so he was always afraid of it, so he would have to face the Ocean one day. which he eventually did (which almost killed him) but made him a man.
However, Kania Tiko (awesome name by the way lol) was right about the meaning as well. Its the more popular meaning used by kids.