1. Phrase chanted at someone to encourage them to skull their drink. Often prompted by discreet drink evasion or whining about how they can't skull or have work the next day. The phrase conveys both an implied threat and disgust in the party it is directed at.
2. To a lesser extent may replace phrase "man up" when someone is piking on a particular activity or event"
"Same again mate?"
"Nah, I think i'll take it easy from now on, I've got work tomorrow."
"Fucking chang up son!"