'aphthae' originates from Greek, specifically the word 'aphthē' (ἀφθα), where the root meant 'a sore, ulcer' or 'that which eats away'.

'aphthae' entered Latin as 'aphthae' from Greek 'aphtha' and was borrowed into English in medical usage as the plural form of 'aphtha'.

Initially it referred to an ulcerative lesion (especially in the mouth); this basic sense has been retained in modern usage as the term for oral ulcers.