Also found in: Wikipedia.
There it is; there you are. A misspelling and mispronunciation of the French "voilà," an exclamation calling attention to or expressing satisfaction with something that has just been presented or accomplished. Finally, you just turn this crank to set it into place and—walla! The machine is ready to go. "Wallah!" said the magician as he pulled the girl's card from his pocket.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
Walla!and Wala! and Wallah! and Viola! (wɑ ˈlɑ)
exclam. And there you have it! (All versions are misspellings or misunderstandings of the French Voila! the Viola! is a well-meant spelling error.) And walla! There it is. Cooked just right!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.