Oreo (n.)

 type of cookie (made by Nabisco), 1912; the source of the name has been forgotten. As a derogatory word for "black person felt to have a 'white' mentality," 1968, African-American vernacular, from the snack cookies, which consist of dark chocolate wafers and white sugar cream filling (hence "brown outside, white inside"). Compare radish-communist (1920), one who proclaims enthusiasm for the Party but privately opposes it, on the notion of red outside, white inside.

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Definitions of Oreo from WordNet

oreo (n.)
chocolate cookie with white cream filling;
Synonyms: oreo cookie