'non-porous' originates from the prefix 'non-' (from Latin 'non', meaning 'not') combined with 'porous', which ultimately comes from Latin 'porosus' and Greek 'poros' meaning 'passage' or 'pore'.

'porous' entered English from Latin 'porosus' (via Old/Middle French forms such as 'poreux'), and the modern adjective 'porous' developed in Early Modern English; adding the productive prefix 'non-' formed the compound adjective 'non-porous' in later English usage.

Originally 'porous' meant 'full of pores or passages' (allowing passage); over time it came to mean 'allowing fluids/gases to pass through', and 'non-porous' developed as the straightforward negation meaning 'not allowing passage' (impermeable).