coolant

Etymology

It is formed from English cool + -ant, on the model of lubricant.^{[2][3][4][5][6]} The OED and the Shorter Oxford take the base as the verb cool, and Etymonline as the adjective.^[2][3][6]

Earliest recorded meaning

A cooling agent: 1915, in a United States patent.^[2][6] Merriam-Webster dates it to 1926, Dictionary.com to 1925–30, and the Oxford Dictionary of English to the 1930s.^[5][7][4]

Semantic evolution

Etymonline glosses the first use as "radiator fluid".^[6] The OED distinguishes two special uses, a liquid that cools and lubricates a cutting tool, and a liquid or gas that carries heat away from an engine or a nuclear reactor.^[2][3]

Timeline

• 1915 – a cooling agent, such as a fluid for an engine.^[2][6]

Meanings

Noun

1. A fluid, liquid or gas, that cools a system or carries heat away from it, as in an engine or a nuclear reactor: Check the coolant before a long drive.^[8][5][2]
2. A liquid used to cool and lubricate a cutting tool and the work during machining.^[8][5][2]

Related words

• cool
• lubricant

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
4. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
5. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins