Green’s Dictionary of Slang

wag n.¹

In phrases

play the wag (v.) [SE wag, a mischievous boy; ult. ? SE waghalter, one likely to end up ‘wagging a halter’, i.e. being hanged]

to play truant.

1841		‘The Charity Boy’ Dublin Comic Songster 164: Vun afternoon I played the vag, / And to the fields my vay did drag.
1856		Eng. Jrnl Education 178/2: Play the wag, hop the charley (v.) to truant.
1880		Bulletin (Sydney) 8 May 4/2: A bad little boy played the wag from a Sandhurst school was thrashed with a hair-brush.
1895		H. Lawson ‘The Master’s Mistake’ in Roderick (1972) 252: Why will you run away from home [...] and play the wag, and steal, and get us all into such trouble?
1900		Bulletin (Sydney) 13 Oct. 30/4: [N]ot far short of 20 per cent. of Victorian children are, at present, habitually ‘playing the wag.’.
1909		H. Lawson ‘The Soldier Birds’ in Roderick (1967–9) II 321: I mind the notes sent home by girls / When someone ‘played the wag.’.
1925		Horsham Times (Vic.) 7 July 4/2: The boy who ‘plays the wag’ need not think that his devious ways of avoiding school [...] goes unwatched.
1937		Sunshine Advocate (Vic.) 23 Apr. 1/3: [headline] Played the Wag. Charles Smith [...] was fined 5/- [...] for failing to send his child to school.
1940		F. Sargeson ‘A Good Boy’ in A Man And His Wife (1944) 71: I pretty often played the wag instead of going to Sunday school.
1951		Cusack & James Come in Spinner (1960) 370: Here we are, after one dance, running away to Luna Park like a couple of children playing the wag.
1959		G. Slatter Gun in My Hand 10: He held the record for breaking windows and playing the wag.