treacherous

Pronunciation

• /ˈtɹɛt͡ʃəɹəs/, /ˈtɹɛt͡ʃɹəs/^[1]

Etymology

It is inherited from Middle English trecherous, also tricherous,^[2][3] borrowed from Anglo-Norman tricherus, also trecherus,^[2][4] and in turn Old French trecheros (“deceitful”), also tricheros,^[5][6][7][8] recorded from the 12th century.^[6][5][4] The Old French adjective is formed from trecheor (“cheat, deceiver”), also tricheor,^[6][5][7] the source of the obsolete English noun treacher,^[5] an agent noun from trichier (“to cheat, trick”), also trechier,^[6][5][7][9] which also gave treachery and, through Old North French, trick.^[6][9] The French verb is of uncertain origin: some scholars cited by the OED refer it to Vulgar Latin *triccō, from Latin tricor (“to be evasive, shuffle”), from tricae (“trifles, nonsense”), and others suggest a Dutch origin or influence.^[6]

Earliest recorded meaning

Of people, false to their oaths or obligations; disloyal, deceitful: about 1330, in Robert Mannyng's Chronicle.^[5][2] Etymonline dates the word to the mid-14th century.^[6]

Semantic evolution

In Middle English it was also used of plans designed to deceive or betray, and as a noun for a treacherous person.^[2] Gower and the Romaunt of the Rose each use it once.^[10] The figurative sense, of things that are deceptive or present hidden dangers, appears in Ben Jonson's The Alchemist (1612);^[5] Etymonline dates it to about 1600, of acts and of things that look fair but cannot be trusted.^[6] Johnson (1755) defined it as "faithless; perfidious".^[11] In Scotland treacherous as Garrick was said of a perfidious person.^[12] In recent slang it has also been used in the reversed sense "excellent, cool".^[13]

Timeline

• c. 1330 – of people, disloyal, deceitful.^[5][2]
• 1612 – of things, deceptive; of ground, water or conditions, dangerous.^[5]

Meanings

Adjective

1. Likely to betray trust; disloyal or deceitful: a treacherous ally.^[14][3][5]
2. Not to be relied on: My treacherous memory let me down again.^[3][14]
3. Having hidden or unpredictable dangers; hazardous: treacherous ice on the bridge.^[14][3][5]

Word family

• treacherously
• treacherousness
• untreacherous

Related words

• treachery
• trick
• trickster
• tricky
• treacher
• intricate
• extricate

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
3. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b Anglo-Norman Dictionary (AND2), Aberystwyth University, anglo-norman.net (2nd ed., 2005–)
5. ^ a b c d e f g h i j k Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
6. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b c Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
8. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
9. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
10. ^ Benson, Larry D., Glossarial Concordance to Middle English (Chaucer, Gower), Johns Hopkins University, github.com/jhu-digital-manuscripts/gcme
11. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
12. ^ Wright, Joseph, ed. (1898–1905), The English Dialect Dictionary, 6 vols., Oxford: Henry Frowde; via EDD Online 4.0, University of Innsbruck (CC BY 4.0)
13. ^ Green, Jonathon (2010), Green's Dictionary of Slang, London: Chambers; digital ed. 2016–, https://greensdictofslang.com
14. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins