'plain-printed' is a compound of 'plain' and 'printed'. 'plain' originates from Old French 'plain(e)', ultimately from Latin 'planus' meaning 'flat, level, clear'. 'printed' derives from Middle English 'printen' (from Old French 'emprimer'), ultimately from Latin 'premere' meaning 'to press'.

'plain' passed from Latin 'planus' → Old French 'plain(e)' → Middle English 'plain'. 'print' developed from Latin 'premere' → Old French 'emprimer'/'emprendre' → Middle English 'printen' → modern English 'print' and past participle 'printed'. The compound adjective 'plain-printed' arose in modern English by combining these elements.

Initially, 'plain' meant 'flat' or 'level' and 'print' referred to making an impression by pressing. Over time, the compound came to mean 'printed in a simple, unadorned manner' — emphasizing clarity rather than physical pressing.