Using the word chicken as slang for crystal meth originated in the city of Indio, CA. what would have been a filling thanksgiving dinner, turned out to be a buffet of narcotics. Nobody ate any turkey cocaine
but they helped themselves to some chicken.
Saying "chicken" instead of "crystal meth" works in your favor when discussing the drug around parents or other people who may not approve of it because one would never suspect chicken means meth.