Term originates from the concept that smoking this kind of cannabis is akin to having an angry Turkish baby thrashing around in your lungs, as Turkish stereotype lends itself to hairy arms and fits of convulsion-inducing rage.
Hence, a small baby with hairy arms thrashing around inside your lungs is a suitable comparison for smoking cannabis fitting the above description.
Also to mention, excessive coughing during smoking any cannabis leads to a more intense high. Adding to this weed's tendency to become more potent the dryer it becomes, Angry Turkish Baby will cause a very severe and lasting high, especially to more virgin lungs.
MAN2: Well, I've got about a 1/4 left over from Halloween last year.
MAN 1: Man, that stuff has become Angry Turkish Baby by now.
MAN 2: Beggars can't be choosers. Try not to loose your bag next time, moron.