chlamydia

Etymology

It is borrowed from New Latin chlamydia, the genus name,^[2][3][4][5] from Ancient Greek χλαμύς (khlamús, “short cloak, mantle”), stem χλαμύδ- (khlamúd-),^[2][3][6] with the New Latin suffix -ia.^[3][5][6] Merriam-Webster Unabridged notes that it follows the earlier genus name New Latin Chlamydozoon.^[3] According to the American Heritage Dictionary and Etymonline, the name refers to the mantle-like form the bacterium takes around the nucleus of the host cell.^[4][6] The Greek word is of uncertain origin; the OED thinks it probably related to χλαῖνα (khlaîna, “upper garment”).^[2][6] The same Greek word gave English chlamys.^[4]

Earliest recorded meaning

A bacterium of the genus Chlamydia: 1945, according to the 1989 edition of the OED and Dictionary.com;^[7][5] the current OED and Merriam-Webster Unabridged date it to 1966, from the Annual Review of Microbiology.^[2][3] Etymonline dates the bacterium's name to 1966.^[6]

Semantic evolution

The name of the bacteria passed to the disease: a genital infection caused by them is called chlamydia from 1984.^[2][6] The bacteria also cause trachoma and psittacosis.^[8][9] The adjective chlamydial is recorded from 1967.^[7]

Timeline

• 1945 – a bacterium of the genus Chlamydia.^[7][5] The current OED dates this sense to 1966.^[2][3]
• 1984 – a genital infection caused by chlamydia bacteria.^[2][6]

Meanings

Noun

1. A bacterium of the genus Chlamydia, small gram-negative parasites that live inside cells and cause diseases such as trachoma.^[3][8][2]
2. A common, often symptomless sexually transmitted disease caused by one of these bacteria.^[3][2][6]

Word family

• chlamydial

Related words

• chlamys

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
5. ^ a b c d Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b c Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press
8. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins
9. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press