'unattenuated' is formed in English by the prefix 'un-' + 'attenuated'. 'Attenuated' comes from Latin 'attenuare', from 'ad-' (to, toward) + 'tenuare' (from 'tenuis' meaning 'thin').

'attenuare' (Latin) passed into Late Latin as 'attenuatus' and into English via French/Latin influence as 'attenuate' in the 17th century; English then formed 'attenuated' and finally 'unattenuated' by adding the negative prefix 'un-'.

Initially related to making something thin or reducing its strength ('to make thin'), the sense broadened to general reduction in intensity or concentration; 'unattenuated' therefore means 'not reduced' or 'not weakened' in modern usage.