'brontosaurus' originates from New Latin/Greek, specifically from the Greek words 'brontē' meaning 'thunder' and 'sauros' meaning 'lizard' (literally 'thunder lizard'); the name was coined in the 19th century by O. C. Marsh.

The name 'Brontosaurus' was originally applied by O. C. Marsh in 1879 ('Brontosaurus excelsus'). Later taxonomic work placed it as a junior synonym of 'Apatosaurus' (named 1877), so 'Brontosaurus' fell out of formal use for many decades; a 2015 study (Tschopp et al.) argued for reinstating Brontosaurus as a distinct genus, leading to renewed usage in some scientific and popular sources.

Initially coined as a literal name meaning 'thunder lizard' for a particular sauropod species; over time it came to represent both a specific genus (with changing taxonomic status) and, more loosely, any very large long-necked dinosaur in popular culture.