'aphthongal' originates from Greek, specifically the word 'aphthongos', where 'a-' meant 'not' and 'phthongē' meant 'sound'.

'aphthongal' was formed in Modern English by combining the Greek root 'aphthongos' with the adjectival suffix '-al' (via Neo-Latin/technical coinage), producing the adjective meaning related to 'lack of sound'.

Initially the Greek term meant 'without sound' and this core sense has been retained in English as 'silent' or 'voiceless'.