Full of piss and vinegar

Meaning

Rowdy, boisterous, full of youthful energy.

Origin

The earliest citation I've found is from 1938 in John Steinbeck's The Grapes of Wrath:

Grampa walked up and slapped Tom on the chest, and his eyes grinned with affection and pride. "How are ya, Tommy?"
"O.K.," said Tom. "How ya keepin' yaself?"
"Full a piss an' vinegar," said Grampa.

There are other similar phrases that came before that which may be the source.

In 1922 Joyce has this in Ulysses - "All wind and piss like a tanyard cat."

As far back as 1602, in Return from Parnassas - "They are pestilent fellowes, they speake nothing but bodkins, and pisse vinegar."

Those earlier citations appear to indicate a more negative meaning to the phrase. 'Wind and piss', or as it is more often given 'piss and wind' is usually taken to mean empty talk, full of bombast. Vinegar is associated with sourness and acidity in many other citations. Peter B. Kyne's 1922 novel They Also Serve includes what seems to be a straightforward polite alternative to 'piss and vinegar':

"He's full of pep and vinegar and wild for exercise."

Vinegar has been in the language as the name of the familiar liquid since the 12th century. During the 1920s vinegar was used to mean vitality and energy and that's the meaning in 'piss and vinegar' and 'pep and vinegar'. At that time many phrases indicating a general perkiness and vitality entered the language, often for no other reason than linguistic exuberance. It's most likely that the phrase originated around then, possibly as an adaptation of the existing 'vig and vigour', which means much the same.