I saw a friend use the word Voila' recently and gave her kudos for it. More often than not, you see people simply spell it the way it sounds: Wallah. Or something like that. Which is way incorrect.
Nope, it's not "wallah," ma petite. It's French! Break it down for us, dictionary.com:
interj. Used to call attention to or express satisfaction with a thing shown or accomplished: Mix the ingredients, chill, and—voilà!—a light, tasty dessert.
[French : voi, second person sing. imperative of voir, to see (from Old French; see voyeur) + là, there (from Old French la, lai, probably from Latin illāc, by that way : illā, ablative sing. feminine of ille, that; see al-1 in Indo-European roots + -ce, deictic particle).]
Okay, now if you're like most people you probably skipped that whole second paragraph (didn't you?!) so I want to point out the origin because it's kind of interesting. Voi means "to see" and la' means "there."
So when you say Voila'! you're literally saying, in French, "See there!" Kind of like "Ta-DA!"
Yay! So be sure you spell it the fancy French way and pronounce it with the "V" sound at the beginning. You want to be sure to get the full effect, ma cherie. *kees, kees* Ciao!