Originally Posted by rc408
I've always wondered why YYZ was the code for Toronto. I like it but that's probably because I'm a Rush fan.

Here's a plausible explanation:
I believe that the Y-designate codes are for radio transmitters from the trans-national service that was originally set up. Hence YYZ, the code for the village of Malton, where the present day LB Pearson international airport is.
Doesn't explain why "YZ" has anything to do with Malton, but ...
Quoted from
http://www.airlinequality.com/Interact/Q1_J00135.htm