a liquid: a source of destructive power accessible to an aggressor: usually referred to as a quantity of whupass ( as in a can of... or bucket of... ). Use of whupass implies that destruction of the aggressor's foe will be a complete immolation of some sort.
"I'm gonna rip open a bucket of whupass and pour it all over you."
A can you would open up to kick someone's ass. Metaphorically.
Really it means, basically, to beat someone up.
"Boy ah' tell you what, if you hit that there snooze button one more time, ah'm goh have ta' open up a can'uh whupass, and you know ah'm goh do it too."
-a cowboy who threatens me if I don't wake up, after hitting the snooze button on my clock four times