dope: [19] Dope originated in the USA, where it was borrowed from Dutch doop ‘sauce’. This was a derivative of the verb doopen ‘dip’, which is related to English dip. It was at first used as a general colloquialism for any thick semi-liquid preparation, whether used as a food or, for example, as a lubricant, but during the 19th century some specific strands began to emerge: notably ‘drug’, and in particular ‘opium’, and ‘varnish painted on the fabric of an aircraft’.
The effects of the former led to its use in the sense ‘fool’, and to the coinage of the adjective dopey, first recorded in the 1890s. The sense ‘information’ dates from around 1900. => deep, dip
dope (n.)
1807, American English, "sauce, gravy, thick liquid," from Dutch doop "thick dipping sauce," from doopen "to dip" (see dip (v.)). Extension to "drug" is 1889, from practice of smoking semi-liquid opium preparation. Meaning "foolish, stupid person" is older (1851) and may have a sense of "thick-headed." Sense of "inside information" (1901) may come from knowing before the race which horse had been drugged to influence performance. Dope-fiend is attested from 1896.