Originally (during the 18th century): a council or assembly, especially in a Dutch-speaking region of South Africa; specifically (usually with capital initial) the legislative assembly of any one of the former Boer republics (now historical). Subsequently (specifically among Afrikaans speakers): any council or board.
Late 18th century; earliest use found in Joseph Banks (1743–1820), naturalist and patron of science. Partly from from Dutch raad council, and partly short for Volksraad.
An electric catfish; especially Malapterurus electricus, found in the Nile and in other rivers and swamps of central and western tropical Africa.
Mid 19th century; earliest use found in John Gardner Wilkinson (1797–1875), Egyptologist. Either from Arabic raʿʿād, lit. ‘thunderer’ or from Arabic raʿd (in samakat al-raʿd, lit. ‘thunder-fish’).