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caustic

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Etymology and origin of the English word caustic

Confidence
Established
Formation
Borrowing
First attested
1400 before 1400, translation of Lanfranc More words from the 14th century
Borrowed from
Latin causticus via Middle English
Ultimate origin
Ancient Greek καίω

Pronunciation

  • UK: /ˈkɔːstɪk/, /ˈkɒstɪk/[1]

Etymology

It is inherited from Middle English caustik,[2] borrowed from Latin causticus (“burning, corrosive”),[3][4][2][5] from Ancient Greek καυστικός (kaustikós, “capable of burning”),[3][4][6] from καυστός (kaustós, “burnt, combustible”),[3][4][6] a verbal adjective of καίειν (kaíein, “to burn”).[3][4][7] Barnhart allows that it came perhaps through Old French caustique,[6] and Klein and Hoad give the French word as a source;[8][7] the OED only compares it, dating Middle French caustique to 1370.[3] The Greek verb is of unknown origin according to the OED,[3] and Etymonline finds no certain cognates outside Greek;[4] Barnhart and Klein derive it from Proto-Indo-European *kēu- (“to burn, heat”),[6][8] comparing Lithuanian kūlė (“blight, mildew”).[8][9]

Earliest recorded meaning

Of a medical agent, burning or destroying tissue: before 1400, in a translation of Lanfranc's Science of Cirurgie.[3][6] Etymonline has about 1400,[4] Merriam-Webster the 14th century.[9]

Semantic evolution

The word entered English in surgical writing, for what burns living tissue, and the noun for such an agent followed before 1425.[3][6] Chemists took it up in 1661 for strongly alkaline substances, and the Shorter Oxford lists caustic soda and lunar caustic.[3][5] The optical sense, of a curve or surface touching the rays reflected or refracted by a lens or mirror, appears in English in 1704; post-classical Latin had used the word for such an intensely luminous curve by 1690.[3] The figurative "cutting, sarcastic" is recorded in 1735 in J. Ozell's translation of a work by d'Allainval,[3] though Barnhart and Etymonline date it from 1771, Barnhart naming Smollett.[6][4] The French adjective had this sense in 1690.[3] The noun had already been used figuratively before 1634, of something that acts like burning.[3]

Timeline

  • before 1400 – in medicine, burning or destroying tissue.[3][6]
  • before 1425 – noun, a caustic agent.[3][6]
  • before 1634 – noun, figuratively, something with an effect like burning.[3]
  • 1661 – in chemistry, strongly alkaline and corrosive.[3]
  • 1664 – burning, fiery.[3]
  • 1704 – in optics and mathematics, adjective and noun, of a curve or surface formed by reflected or refracted light.[3]
  • 1735 – of humour or words, cutting, scathing.[3] Barnhart and Etymonline date it to 1771.[6][4]
  • 1779 – noun, a strong corrosive alkali.[3]
  • 1830 – verb, to treat a part of the body with a caustic (obsolete by 1918).[3]

Meanings

Adjective

  1. Able to burn or corrode living tissue or other material by chemical action: a caustic oven cleaner.[10][9][3]
  2. Strongly alkaline.[9][3]
  3. Bitingly sarcastic or scathing: her caustic remarks about the budget.[10][9][3]
  4. (optics) Of or formed by light reflected or refracted by a curved surface.[10][3]

Noun

  1. A substance that burns or corrodes organic tissue.[10][9][3]
  2. A strong alkali, as sodium hydroxide.[9][3][10]
  3. (optics) A curve or surface formed by reflected or refracted rays.[10][9][3]

Word family

  • caustically
  • causticity
  • catacaustic
  • diacaustic
  • noncaustic
  • caustic curve
  • caustic potash
  • caustic soda

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z 27 28 29 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  4. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  5. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  6. ^ a b c d e f g h i j Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  7. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
  8. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
  9. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  10. ^ a b c d e f Collins English Dictionary (2023), Glasgow: HarperCollins

Related etymologies

Cite this entry

“Caustic.” Etymologically, 5 Nov. 2026, etymologically.com/en/caustic. Accessed 6 Nov. 2026.

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