impervious

Etymology

It is borrowed from Latin impervius (“having no way through, impassable”),^{[2][3][4][5][6]} with the English suffix -ous.^[2][4][7] The Latin adjective is formed from in- (“not”), here assimilated as im-, and pervius (“letting things through, passable”),^[3][4][5][6] the source of pervious.^[5][4] The second part comes from per (“through”), from Proto-Indo-European *per- (“forward, through”), and via (“road, way”).^[3]

Earliest recorded meaning

Not letting water, air or light pass through; impenetrable: 1615, in H. Crooke's anatomy Mikrokosmographia, the first record found by the OED, revised in 2019.^[2] Merriam-Webster Unabridged dates the word to 1640, Etymonline to the 1640s and Barnhart to 1650.^[8][3][4]

Semantic evolution

In 1618 the word was also used for "hard to understand, unfathomable", a sense the OED records until 1794.^[2] From 1650 it was used of things not affected by something, especially something harmful,^[2] and the Shorter Oxford likewise dates the figurative use to the mid 17th century.^[9] Johnson (1755) defined it as "unpassable; impenetrable", quoting Boyle on a thin film of glass impervious to the air.^[10] The sense "not open to argument or persuasion", of a person or a mind, is recorded from 1823.^[2]

Timeline

• 1615 – not letting water, air or light through; impenetrable.^[2] Merriam-Webster Unabridged dates this sense to 1640 and Barnhart to 1650.^[8][4]
• 1618 – hard to understand, unfathomable (obsolete by 1794).^[2]
• 1650 – not affected by something, especially something harmful.^[2]
• 1823 – of a person, not open to argument or persuasion.^[2]

Meanings

Adjective

1. Not letting water, air, light and the like pass through; impermeable: The tent's floor is impervious to damp.^[11][8][2]
2. Not able to be damaged or harmed by something: a floor coating impervious to most chemicals.^[8][2]
3. Not affected or influenced by something; not open to argument or persuasion: He seemed impervious to their pleas.^[11][8][2]

Word family

• imperviously
• imperviousness

Related words

• pervious
• via

Usage notes

Collins and Dictionary.com also record the rarer form imperviable.^[11][12]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
6. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
7. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
8. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
10. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
11. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
12. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House