flex

Pronunciation

• /flɛks/^[1]

Etymology

It is borrowed from Latin flexus (“bent”), the past participle of flectō (“to bend”),^[2][3][4] or its stem flex-.^[5][6][7][8] Etymonline instead takes it as probably a back-formation from flexible.^[9] According to Klein, Ernout and Meillet considered flectō perhaps a popular by-form of plectō (“to plait, braid”).^[3] The British noun flex, an electric cord, is a separate shortening of the same adjective (a flexible cord or cable), recorded from 1905.^{[5][2][7][10]}

Earliest recorded meaning

To bend: the OED's first quotation is from the romance Helyas (before 1521);^[5] Merriam-Webster dates it to 1521,^[2] and Etymonline to the 1520s, usually of muscles.^[9]

Semantic evolution

For centuries the verb was transitive and chiefly scientific, used of bending a joint or limb by the flexor muscles, as opposed to extend.^[5][6] The intransitive use, to bend, or of a muscle to contract, is first recorded in Webster's dictionary of 1909 and was originally American.^[5] The figurative flex one's muscles, to make a show of strength or aggression,^[6][4] led to the sense "to use or demonstrate (power)".^[2] In mathematics flex became a noun for a point of inflection in 1866.^[5][6] The electrical flex of 1905 is a clipping of flexible,^[5][6] described by Weekley in 1921 as a neologism for the covered wire of an electric lamp.^[11] From the late 1980s American slang used the verb for leaving (1987), for getting ready to fight, and for showing off (1991), and the noun for courage or nerve (1992);^[12] Collins records the slang sense "to flaunt one's possessions or attributes".^[4] With flexitime, flex also came to mean working flexible hours.^[4]

Timeline

• 1521 – to bend.^[2][5]
• 1866 – noun, in mathematics, a point of inflection.^[5]
• 1905 – noun, a flexible electric cord (shortened from flexible).^[5][2]
• 1909 – intransitive, to bend; of a muscle, to contract.^[5]
• 1987 – American slang, to leave.^[12]
• 1991 – American slang, to show off.^[12]
• 1992 – slang noun, nerve, courage.^[12]

Modern meaning

Verb

1. To bend something, especially a joint or limb: She flexed her fingers to warm them.
2. To contract a muscle, or of a muscle, to contract.
3. To test or display one's authority or strength.
4. flex one's muscles: to make a show of power.
5. To work according to flexitime.
6. (US slang) To flaunt one's possessions or qualities; to show off.

Noun

1. (chiefly British) A flexible insulated electric cable connecting an appliance to the mains; in American English, a cord.
2. An act of flexing.
3. (informal) Flexibility.
4. (mathematics) A point of inflection.

Related words

• flexible
• flexion
• reflex
• deflect
• inflect
• reflect
• circumflex
• retroflex

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
3. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
4. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins
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 Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
9. ^ a b Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
10. ^ Cresswell, Julia (2021), Oxford Dictionary of Word Origins, 3rd ed., Oxford: Oxford University Press
11. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
12. ^ a b c d Green, Jonathon (2010), Green's Dictionary of Slang, London: Chambers; digital ed. 2016–, https://greensdictofslang.com