incest

Etymology

It is inherited from Middle English incest,^[2] borrowed from Latin incestus (“unchastity, incest”) or incestum, both nouns formed from the adjective incestus, impure, unchaste.^[3][4][5][6] The adjective is formed from in- (“not”) and castus (“pure, chaste”), the source of chaste,^[3][7][8] which the American Heritage Dictionary traces to Proto-Indo-European *kes-.^[4] Klein takes the second part instead as the Old Latin noun castus, chastity, which is related to the adjective.^[9] Barnhart and Etymonline see it as coming partly through Old French inceste (“incest; lechery, fornication”),^[10][11] but the OED records the French word only from the 14th century.^[3] Old English had sibleger (“incest”), literally "kin-lying".^[11][12]

Earliest recorded meaning

Sexual intercourse between persons too closely related to marry: first recorded about 1225, in the Ancrene Riwle,^[3][10] which Barnhart dates to probably before 1200.^[10] Etymonline dates the word to about 1200.^[11]

Semantic evolution

Ayto notes that the Latin word meant unchastity in general, but was in practice often used of sex between close relatives,^[7] and the Old French word could also mean lechery or fornication.^[11] In English the first records already have the narrow sense, and the same early text it also appears in spiritual incest, a term of the Roman Catholic Church for a sexual relation between people joined by a spiritual bond or involving someone under a vow.^[3] Chaucer used the noun.^[13] From 1484, in Caxton's translation of Aesop, incest could also name a person guilty of incest, a sense now obsolete.^[3][14] The adjective incestuous followed in 1532, in Sir Thomas More.^[10][8] Johnson (1755) defined incest as a criminal union of persons within the prohibited degrees, quoting Measure for Measure.^[15] In law it is now specifically the crime of intercourse between parent and child or grandchild, or between brothers and sisters.^[5]

Timeline

• c. 1225 – sexual intercourse between near relatives, and spiritual incest, in the Ancrene Riwle.^[3]
• 1484 – a person guilty of incest (now obsolete).^[3][14]
• 1532 – the adjective incestuous, in Thomas More.^[10]

Meanings

Noun

1. Sexual intercourse between people so closely related that they are not allowed to marry: The novel deals frankly with incest in a remote village.^[16][6][3]
2. (law) The crime of sexual intercourse between a parent and a child or grandchild, or between brothers and sisters or half-siblings.^[5][3]

Word family

• incestuous

Related words

• chaste
• caste
• castigate
• unchaste

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ Stratmann, Francis Henry (1891), A Middle-English Dictionary, revised by Henry Bradley, Oxford: Clarendon Press
3. ^ a b c d e f g h i j Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
4. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
5. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ a b Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b Ayto, John (2005), Word Origins: The Secret Histories of English Words from A to Z, 2nd ed., London: A & C Black
8. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
9. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
10. ^ a b c d e Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
11. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
12. ^ Bosworth, Joseph; Toller, T. Northcote (1898), An Anglo-Saxon Dictionary, Oxford: Clarendon Press; Toller, T. Northcote (1921), Supplement
13. ^ Skeat, W. W., ed. (1894), The Complete Works of Geoffrey Chaucer, vol. VI: Glossarial Index, Oxford: Clarendon Press
14. ^ a b Kay, Christian; Roberts, Jane; Samuels, Michael; Wotherspoon, Irené, eds. (2009), Historical Thesaurus of the Oxford English Dictionary, Oxford: Oxford University Press; online edition (2024)
15. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
16. ^ Collins English Dictionary (2023), Glasgow: HarperCollins