'undecorated' originates from the prefix 'un-' meaning 'not' and the word 'decorated' from Latin 'decoratus', where 'decorare' meant 'to adorn'.

'decoratus' transformed into the English word 'decorate', and with the addition of the prefix 'un-', it became 'undecorated'.

Initially, it meant 'not adorned', and this meaning has remained consistent in modern usage.