Dope is from the Dutch word doop, meaning a thick sauce, and became a drug term from the semi-liquid form of opium smoked by drug addicts.
The use of dope meaning “stupid” came from the retarded behavior of someone under the influence of the drug.
The use of “the real dope” as information came in around 1900 when gamblers checking on racehorses needed to know whether or not any of the horses were drugged or doped.
