The operator was introduced by the Irish mathematician Sir William Hamilton (1806–65), who represented it by the symbol ◁. It was named ‘nabla’ at the suggestion of W. Robertson Smith.
Late 19th century; earliest use found in William R. Smith (1846–1894), theologian and Semitic scholar. From Hellenistic Greek νάβλα Phoenician harp. This word was applied to the operator because of the similarity between the assumed shape of the musical instrument and the symbol used.