Etymology of "chookas"

The Concise New Partridge Dictionary of Slang and Unconventional English (2007) says:

chookas! used for wishing an actor good luck. Actors are, by tradition, superstitious , and to actually wish an actor 'good luck' in so many words is thought to be tempting fate; this abstract (derivation unknown) or surreal benediction was used by Evan Dustan, an Australian theatrical agent during the 1980s. AUSTRALIA, 1984

As per this post from 2006 in an Aussie theatre forum, Joe McCabe provides a similar story:

I first came across it at the old firm of JCW’s way back in a prestroke life.

There was a poem that went with it, but I can’t remember it now. The bit I do recollect is the complete term is ‘Tio Tio Tio Chookas’ loosely meaning ‘With hear & sole. May you always play to a full house’

Also the actions which go with the poem, were using your right hand, pat your left heart 3 times with the words ‘tio’ & jump up on ‘Chookas’.

There are still a few old members of the ‘Firm’ & possibly some still on the perch, that played the ‘halls’ back in the 1900’s.

Who may remember the old poem?

But Chookas was derived during the days of the ‘Halls’. At a time when it was considered a delicacy to have a meal of chook & it could cost almost a good weeks pay, unless you were lucky enough to be in digs that had them in the back yard.

At best the ‘Coolgardie safe’ or if the Iceman cometh, was the only way to keep meat generally.

On the halls & indeed with most theatre productions performance fees paid depended on the box office take for the performance, Much the same as little jonny would like to do & virtually come in full circle - so there is nothing new there in the IR laws!

Apparently the SM or Manager would check the house before the ‘Beginners Ready’ cue & advise if they were to have chook to night or not. Hence the call would go around back stage, something like "chook it is" tonight everyone, which became shortened to chookas after a while.

Supposedly’ Tio Tio Tio’ was added with the influx of European performers around that ttime, suggested to mean ‘With heart & sole’! This would also falls in line with the old chook raffles of the time, when the publican or whoever was running it, would create interest in the raffles by continually calling out various things from chooks to chookas!

To summarise, the story provided appears to concur with the "Behind Ballet" blog post. Joe McCabe mentions both J.C. Williamson as well as the "chicken tonight" aspects with a note that it might have been popularised by a song that also incorporated "toi, toi, toi", a similar phrase which also finds mention in the WP article. But, he observes as an afterthought that the call of "chookas" might have already been associated with chook raffles.