1) A girl's name. Not very common but still used.
2) A slang term to refer to
cocaine. The term "Chloe" comes from the fact that
cocaine also starts with an "C" and many other drugs use girls' names as slang for their respective drug.
Chloe is sometimes used as a code word for
cocaine when referring to the drug in a public setting or over the phone where one does not want to openly discuss illegal activities.
Chloe is used like a person's name in such discussions. Like saying "When Chloe is around I am always happy" to indicate that when cocaine is readily available this person is always in a "happy" or euphoric state.