> > > http://www.urbandictionary.com/define.php?term=wallah > > > > Funny how UD is the only site to make any kind of reference to that meaning. > > You're just getting old and out of touch. Slang changes every generation.
This has nothing to do with changing slang. The urban dictionary entry doesn't even apply here because it doesn't mean the same thing. It's just coincidence.
Voilà, which is a contraction of vois là (literally means "see there"), is often used in English at the end of a sentence where it translates roughly as "there you have it".
It's very common for English speakers who have only ever heard voilà spoken to write it phonetically as walla or wallah.