'anguillid' originates from New Latin, specifically the word 'Anguilla' (from which the family name 'Anguillidae' is formed), where 'Anguilla' meant 'eel'.

'anguillid' changed from Latin 'anguilla' (meaning 'eel') into New Latin taxonomic usage 'Anguillidae' for the family, and then into the English noun 'anguillid' to denote a member of that family in scientific contexts.

Initially it referred to the Latin term for 'eel'; over time it evolved into a modern English zoological term meaning 'a member of the family Anguillidae (a freshwater eel)'.