'plainly-decorated' originates from the combination of 'plainly' and 'decorated', where 'plainly' means 'in a simple manner' and 'decorated' means 'adorned or embellished'.

'plainly-decorated' combines the Middle English word 'plain' from Old French 'plain' and the past participle 'decorated' from Latin 'decoratus'.

Initially, 'plainly' meant 'clearly' or 'simply', and 'decorated' meant 'adorned'. Together, they evolved to describe a style that is simple yet adorned.