'anisognathous' originates from Greek, specifically the word 'anisognathos', where 'aniso-' meant 'unequal' and 'gnath-' meant 'jaw'.

'anisognathous' came into scientific English via New Latin or Neo-Greek formations (e.g. New Latin 'anisognathus') in the 19th century, built from Greek components and used in anatomical and zoological descriptions.

Initially it meant 'having unequal jaws' in technical anatomical usage, and this specific sense has been retained in modern scientific contexts.