yolk

Etymology

It is inherited from Middle English yolke, also yelke,^[2][3][4][5] inherited from Old English ġeolca, also ġeoloca and ġeoleca,^[4][5][3][6] literally “the yellow part”,^[2][4] a derivative of ġeolu (“yellow”), the source of yellow,^{[2][4][7][8][9]} with a suffix that the OED takes to be probably the one in -ock and Wiktionary a diminutive.^[10][1] The OED explains the diphthong of the Old English word by back mutation, and the later spellings as different developments of this diphthong, probably also influenced by the forms of yellow.^[10]

Earliest recorded meaning

The yellow inner part of an egg: early Old English, in Bald's Leechbook;^[10] Barnhart dates the Old English word to before 1000.^[4] Ælfric used it in a homily: “look now on an egg, how the white is not mingled with the yolk, and yet it is one egg”.^[6]

Semantic evolution

Barnhart's first Middle English record is the spelling yelke, before 1325, and yolke appears before 1398.^[4] From 1340, in the Ayenbite of Inwyt, the word was used figuratively for the core or innermost part of anything.^[10] Johnson (1755) defined it simply as “the yellow part of an egg”, referring readers to yelk.^[11] Later senses were technical: a hard nodule in rock or coal (1665–1886, from Hooke's Micrographia), the perisperm of a seed in botany (1795–1842), and in biology the part of any ovum that feeds the embryo (from 1817).^[10] In Scotland the thick opaque centres of panes of window glass were called yolks, from their likeness to the yolk of an egg.^[12][10]

Timeline

• before 1000 – ġeolca, the yellow of an egg.^[10][4]
• before 1325 – the Middle English spelling yelke.^[4]
• 1340 – figurative, the core or heart of something.^[10]
• before 1398 – the spelling yolke.^[4]
• 1665 – a nodule in rock or coal (obsolete by 1886).^[10]
• 1795 – in botany, the perisperm of a seed (obsolete by 1842).^[10]
• 1802 – in Scotland, a thick round part of a pane of glass.^[10][12]
• 1817 – in biology, the nourishing material of an ovum.^[10]

Meanings

Noun

1. The yellow inner part of the egg of a bird or reptile, surrounded by the white: Beat two yolks with the sugar.^[3][13][10]
2. (biology) The material in an ovum, rich in protein and fat, that nourishes the developing embryo.^[13][10][9]
3. The innermost or most essential part of something; the core.^[10]

Word family

• yolky
• yolked
• yolkless
• yolk sac

Related words

• yellow
• gold

Usage notes

Merriam-Webster records the pronunciation /ˈyelk/ in cultivated speech, especially in the American South.^[3] The OED notes that /jɛlk/ was reported by several early modern writers on pronunciation, that Noah Webster in 1789 called it the general American pronunciation, and that the spelling yelk was used in print into the early 20th century.^[10] Yolk is also the name of the greasy substance in a sheep's fleece, recorded from 1767.^[10][13] The OED treats it as a separate word, apparently from an unrecorded Old English *ēowoc, related to ewe, with its spelling influenced by the egg yolk;^[10] the Shorter Oxford takes it as a back-formation from yolky.^[9]

References

1. ^ a b c Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c d e f g h i Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b Bosworth, Joseph; Toller, T. Northcote (1898), An Anglo-Saxon Dictionary, Oxford: Clarendon Press; Toller, T. Northcote (1921), Supplement
7. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
9. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
10. ^ a b c d e f g h i j k l m n o p q r Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
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. ^ a b 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. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins