'apatosaurus' originates from New Latin, formed from the Greek words 'apate' and 'sauros', where 'apate' meant 'deceit' and 'sauros' meant 'lizard'.

'apatosaurus' was coined in the late 19th century (by O. C. Marsh in 1877) as a New Latin scientific name from Greek elements; it entered English scientific usage as the genus name for certain large Jurassic sauropods and was later involved in taxonomic discussions with the name 'Brontosaurus'.

Initially it literally meant 'deceptive lizard' (from the Greek roots), but over time it evolved into a taxonomic name for a genus of large Jurassic dinosaurs and no literal sense of 'deceit' is intended in common use.