Go for ?IT? Slickster!
If I may just mention the old adage[Circa;- today]

 "You can see more with your ears -

If you listen with your eyes!"

Which inturn relates also to;-

 "hear the Light & see the Sound!"
{but that?s another story from the ?Naked chook pen?.}

I believe Toi is a hang up from European theatre, loosely meaning with or from the heart. It is said while patting  your right hand on your left heart (if you have more than one?)  each time Toi is said. Chook means chicken in the strine lingo. Chookas came about during the music Hall/Vaudeville days. Meaning as we have a full house we will be all eating chicken tonight.  Remembering in those days, chicken was an expensive meat in the Cities. Because the only refrigeration available was from an ice chest or meat safe. The meat safe was an open framed cabinet with a water container on top. Hessian draped over it & submerged into the container at the top. The water would soak down thru the weave of the material via a capillary action & the air would  evaporate the  breeze cooled water drawn down thru the hessian. In the same way as water coolers & evaporative air condition units work today - only much cruder. So unless you grew chickens in your back yard, where they could be harvested, cooked & eaten in the hot weather. It was a rarity for itinerant performers to afford to eat chicken. Hence the call from the SM, that it was a full house! Became chookas. Now a days it is a good luck wish & hope you  play to a full house.
Simular to ?Break a leg? which originated about the same time for different reasons. But that?s another story!

 Me thinks this may be more appropriate to be under a topic on ?Theatrical Terms??
Like what?s the meaning of Green Room/ Gage/ Sward - Teasers ?n Tormentors - Gobo?s & others?

But in an attempt to answer your request!
The only plausible origin of ?Break a leg? I have thus far tripped over! Comes from the advent of Variety shows such as Music Hall that latter turned into Vaudeville - Which arguably came from French {"vaux de ville" ("worth of the city)}.
 Not as some suggest that it was from dear Old Bill?s time in Southwalk at the Globe Theatre. Which was supposed to be if you were  to ?break a leg? this was to bow?  As mentioned in one of his scripts. Unfortunately I doubt that this is the case  - as what was possibly stated , was as a stage direction or blocking move - ? break to a leg bow? or something simular. Remembering in most cases a lot of actors of the time could hardly  read -if at all. Therefor most of his original scripts were learnt parrot fashion & nearly all were lost, written by scribes during the rehearsals &/or re-written much later.
Break a leg didn?t really come into vogue or recorded as a general theatre term - until around the 1800?s.
Theatres who provided variety style shows for mass appeal. Would attempt to have on stand by as many different acts& performers  as possible, to fill their Bill for a performance. It was not viable to pay each stand by act, if they didn?t actually appear on stage. Therefore a policy of if you didn?t actual get to break the visual plane of the Leg line  (Wing masking)  - You don?t get paid! Similarly you would only receive nominal ?appearance money? if your performance got the ?hook?!
On that note - I better give my book the ?hook?!?!