'athematic' originates from Greek elements: the privative prefix 'a-' (meaning 'not' or 'without') and the noun 'thema' (Greek 'θέμα') meaning 'that which is set' or 'a theme'.

'thema' passed into Late Latin/Medieval Latin as 'thema'/'thematicus' and into English as 'thematic'; the Modern English adjective 'athematic' was formed by adding the Greek-derived privative 'a-' to 'thematic'.

Originally denoting simply 'not thematic' or 'without a theme', the term became specialized in linguistic description to mean specifically 'lacking a thematic vowel' (as in athematic verbs).