'unwashed' originates from English, formed by the prefix 'un-' (from Old English 'un-' meaning 'not') plus the past participle of 'wash' (Old English 'wascan') where 'wascan' meant 'to wash'.

'wash' developed from Old English 'wascan' into Middle English forms such as 'waschen'/'washen'; the negative prefix 'un-' (Old English/Germanic) combined with past participle forms (e.g. Middle English 'unwaschen') to give the modern English adjective 'unwashed'.

Initially it literally meant 'not washed' (i.e. not cleaned). Over time it also acquired a figurative/social sense referring to those considered uncultured or common—the phrase 'the unwashed' for the masses.