'unrhymed' originates from English, specifically the prefix 'un-' (from Old English 'un-' meaning 'not') combined with the word 'rhyme' (from Old French 'rime').

'rhyme' changed from Old French 'rime' (borrowed into Middle English as 'rime') and ultimately from Latin 'rhythmus' and Greek 'rhythmos' meaning 'measured flow'; the negative prefix 'un-' was added in English to form 'unrhyme' and adjectives like 'unrhymed' in Modern English.

Initially the root related to 'measured flow' (Greek 'rhythmos') and then came to mean correspondence of sounds at line ends ('rhyme'); adding 'un-' produced the straightforward modern sense 'not rhymed', which has remained stable.