Green’s Dictionary of Slang

(US drugs) someone who prepares an opium pipe for use.

1930		J. Lait Gangster Girl 141: The old servitor had been his official cooky for years, had prepared his pipe, rolled his pill and touched it with the magic flame.
1959		J.E. Schmidt Narcotics Lingo and Lore 34: Cooky – An opium den attendant.