'aphasiac' originates from Greek via Neo-Latin/medical formation, specifically from Greek 'aphasia' (ἀφασία), where the prefix 'a-' meant 'without' and 'phasis/ phasia' meant 'speech'.

'aphasiac' developed from Greek 'aphasia' into Neo-Latin/medical forms (e.g. Latinized or French medical usage) and was borrowed into English in the 19th century as the noun for a person affected by aphasia.

Initially related to the condition name meaning 'without speech' (loss of speech), it later came to be used for a person affected by that condition (i.e. 'an aphasiac').