septum

Etymology

It is borrowed from Latin sēptum, also saeptum (“enclosed space, fold, fence, barrier, partition”),^[2][3][4][5] the neuter past participle, used as a noun, of sēpīre, saepīre (“to enclose, hedge in”), from saepēs (“hedge, fence”).^{[2][6][7][8][9]} Etymonline, Barnhart and the American Heritage Dictionary treat the English word as a New Latin use of the Latin noun,^[8][7][6] while the revised OED takes it straight from classical Latin.^[2] The OED calls the origin of the Latin noun for hedge uncertain;^[2] de Vaan, as cited by Etymonline, derives it from Proto-Indo-European *seh₂i- (“to tie”),^[8] and Barnhart and Merriam-Webster Unabridged compare a Greek word for a thicket.^[10][3] The Latin word is also the source of sept in the sense of an enclosure,^[2][11] and Medieval Latin transseptum gave transept.^[11]

Earliest recorded meaning

The diaphragm, more fully septum transversum: 1543, in Traheron's glossary of strange words in a translated surgical work; this sense is obsolete.^[2] Etymonline dates the word to the 1690s,^[8] Merriam-Webster Unabridged to 1698^[3] and Barnhart to 1720.^[7][10]

Semantic evolution

In English the word began in anatomy, as a partition in the body: after the diaphragm, Helkiah Crooke's anatomy of 1615 used it for the wall between the nostrils, the wall dividing the heart and a thin partition in the brain.^[2] Barnhart dates the nasal septum in English to 1726.^[10] Closer to the Latin, it could also mean an enclosure for animals (before 1552, rare) and a partition or dividing wall, formerly also a communion rail (before 1638).^[2][9] From the 18th century it spread to the natural sciences: a partition in a plant (1720), a thin plate dividing a shell (1786) and, in geology, a narrow mineral deposit dividing a body of rock (before 1728).^[2] In 1938 it entered electronics for a metal plate across a waveguide.^[2]

Timeline

• 1543 – the diaphragm (obsolete).^[2]
• before 1552 – an enclosure for animals, a paddock (obsolete).^[2]
• 1615 – the partition between the nostrils; the wall dividing the heart; a partition in the brain.^[2]
• before 1638 – a partition or dividing wall; formerly a communion rail.^[2]
• 1720 – in botany, a partition between parts of a plant.^[2][10]
• before 1728 – in geology, a mineral layer dividing a rock.^[2]
• 1786 – in zoology, a plate dividing a shell.^[2]
• 1938 – in electronics, a plate placed across a waveguide.^[2]

Meanings

Noun

1. A dividing wall or membrane between two cavities or masses of tissue in an animal or plant.^[12][3][2]
2. The nasal septum, the wall of bone and cartilage between the nostrils: She broke her septum playing rugby.^[3][2]
3. (botany) A partition between parts of a plant, as between the cells of a compound ovary.^[3][2]
4. (zoology) A plate dividing a shell into chambers, or a partition between the segments of an annelid.^[3][2]
5. (geology) A thin layer of mineral dividing a larger body of rock.^[3][2]
6. A dividing partition in a mechanical device; in electronics, a metal plate across a waveguide.^[12][2]

Word family

• septate
• septectomy
• septal

Related words

• sept
• transept

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r s t u v w x 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. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
5. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
7. ^ a b c Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
8. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
9. ^ a b 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 Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
11. ^ a b Partridge, Eric (1966), Origins: A Short Etymological Dictionary of Modern English, 4th ed., London: Routledge & Kegan Paul
12. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins