'dolphin' originates from Latin, specifically the word 'delphinus', where 'delph-' came from Greek 'delphís' (δελφίς) meaning 'dolphin' and is related to 'delphús' (δελφύς) meaning 'womb'.

'dolphin' changed from Middle English 'dolfyn' (also Old English 'dolfin') which came from Latin 'delphinus', and eventually became the modern English word 'dolphin'.

Initially, it meant 'a sea creature known as a dolphin', and over time the basic meaning has remained stable though biological classification and understanding of species have become more precise.