a native (not indigenous) of New South Wales (may be archaic and used pejoratively or even abusively. (Can we this quote?) Marshall, Peter, The Cambridge Illustrated History of the British Empire, Cambridge: Cambridge University Press, ISBN 978-0521002547, page 272: ...by 1872 'cornstalk' had become a caustic term for the New South Welsh)
He's a bloody cornstalk. - He is from New South Wales.