'assonant' originates from Latin, specifically the word 'adsonare,' where 'ad-' meant 'to/toward' and 'sonare' meant 'to sound'.

'assonant' passed into Old French (as 'assonant') and Middle English retaining a similar form, eventually becoming the modern English adjective 'assonant' and its adverbial form 'assonantly'.

Initially related to the idea of 'sounding toward' (a literal joining of sounds), it evolved to the current sense of 'having or using similar vowel sounds' (i.e., assonance).