'arachnophobia' originates from Greek, specifically the words 'aráchnē' and 'phóbos', where 'aráchnē' meant 'spider' and 'phóbos' meant 'fear'.

'arachnophobia' was formed in English by combining the Greek root 'arachn-' (from 'aráchnē') with the suffix '-phobia' (from 'phóbos'), a construction influenced by medical and psychological terminology (Modern/Neo-Latin formation entering English usage).

Initially, it meant 'fear of spiders' and over time it has retained that core meaning as the term for that specific phobia.