Green’s Dictionary of Slang

(Aus.) a silent person, one who does not talk.

1948		S.L. Elliott Rusty Bugles II iii: ot.: Cripes. Poor old Dean Maitland. gig.: Is he nuts? [...] vic.: There must have been a lot on his mind. I never saw him speak the whole time he was here.
1969		R.S. Whitington Quiet Australian 98: The twenty-two players were far too tense to talk during the twenty-minute break. Twenty-two ‘Dean Maitlands’ sipped their tea in silence [GAW4].