'plastic-built' originates from Modern English as a compound of 'plastic' and 'built'. 'plastic' ultimately comes from Greek 'plastikos', where 'plast-' meant 'to form or mold'; 'built' is the past participle of 'build'.

'plastic' came into English via Latin/French from Greek 'plastikos' (meaning 'fit for molding') and later came to refer to synthetic polymers; 'build' comes from Old English words such as 'byldan'/'byrgan' (rendered into Middle English as 'bilden'/'builden') and developed into the modern verb 'build' and past participle 'built'. The compound 'plastic-built' is a modern formation combining these elements.

Initially 'plastic' meant 'fit for molding' in Greek and later came to mean 'a material (often synthetic) that can be molded'; 'build' originally meant 'to construct' and has retained that core sense. Combined, 'plastic-built' now means 'constructed of plastic' and sometimes carries a figurative sense of being cheap or mass-produced.