I believe it is a spunky child but when would you use this expression? Do you know where it originates? How does spit go with vinegar?

Did you sanitize that? The way I've always heard it was, is: "p*ss" and vinegar". I assumed it was a variation on "Vim and Vigor". I could be mistaken, it may have been pi** rather than p**s or *iss.??

I've always known it to be spit and vinegar, although it may be both.

I'm thinking:

"Little Billy, your are just full of spit and vinager! Sit down already!"

I don't think many parents say *iss to their kids. (although some may)

So do you know the answer ya potty mouth?

Yeah, p & v. Fer sure.

Musta been like the old ladies who used to say 'sugar' when they had a small domestic disaster: burnt the porridge, whatever. Us kids knew what they really wanted to say!

Some reading material:

http://www.phrases.org.uk/meanings/145600.html
http://www.randomhouse.com/wotd/index.pperl?date=20000308

(no claims made or implied regarding the accuracy of these sources )