Green’s Dictionary of Slang

(Aus./N.Z.) a cunning person.

1909		Examiner (Launceston, Tas.) 16 Nov. 3/5: [C]ontemptible, mean, sneaking, crawling loafers, who hang about the camps, who laugh and boast how they dodge work. To use their own expression, they are the shrewd-heads.
1911		Barrier Miner (Broken Hill, NSW) 24 May 6/1: Anyway. the ‘shrewd heads’ are now backing Jolly Beggar for the City Handicap.
1914		C.J. Dennis ‘The Play’ in Bulletin (Sydney) 16 July 47/1: Now, this ’ere gorspil bloke’s a fair shrewd ’ead. / Sez ’e, ‘I’ll dope yeh, so they’ll think yer dead.’.
1919		W.H. Downing Digger Dialects 45: shrewd head — A cunning person.
1924		(con. WWI) A.G. Pretty Gloss. Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: shrewd head. A cunning person.
1933		(con. WWI) A.E. Strong in Partridge Sl. Today and Yesterday 287: Joe. He is a shrewd head, but I think he would give a man a fair go although he is a base-walloper.
1938		Advertiser (Adelaide) 12 Jan. 27/2: One shrewdhead [...] was the leader of the ‘horse duffing’ gang.
1944		Western Mail 8 June 8/4: He knew his gandparent to be a ‘shrewd-head’ who rarely missed a thing.
1988		McGill Dict. of Kiwi Sl. 102/2: shrewd head [...] a shrewd person.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].