deepen

Etymology

It is formed from English deep + -en.^{[2][3][4][5][6]} It replaced the older verb deep, Middle English depen.^[3][5][7] The adjective is from Old English dēop, from Proto-Germanic *deupaz.^[3][8] The OED compares the similar formations Swedish djupna (18th century) and Danish dybne (19th century).^[2]

Earliest recorded meaning

To make something deeper, to increase its depth: 1589, in Paul Ive's Practise of Fortification.^[2] Merriam-Webster dates the transitive verb to 1598,^[9] Barnhart to before 1605, and Etymonline to about 1600.^[4][3]

Semantic evolution

The intransitive sense, to become deeper, is recorded from 1600 in Hakluyt,^[2] or from the 1690s in Etymonline.^[3] The verb was soon applied to colour (to make a colour deeper, 1606, in Peacham's Art of Drawing, which Johnson quoted for "to darken"), to feelings and states (to make more intense or profound, 1641), and to sound (to become lower in pitch, 1727, in Thomson's Summer).^[2][10] In Shetland dialect deepen also meant to take soundings.^[11]

Timeline

• 1589 – to make deeper.^[2]
• 1600 – to become deeper.^[2]
• 1606 – to make a colour deeper.^[2][10]
• 1641 – to make more intense or profound.^[2]
• 1673 – of a colour, to become deeper.^[2]
• 1699 – to become more intense, in a letter of Pepys.^[2]
• 1727 – of a sound, to become lower in pitch.^[2]
• 1749 – to make a sound or voice lower.^[2]

Meanings

Verb

1. To make or become deeper in extent; to increase the depth of: The engineers deepened the harbour for larger ships.^[12][9][2]
2. To make or become more intense or profound: Their friendship deepened over the years.^[12][9][2]
3. Of a colour, to make or become darker or richer.^[2][9][10]
4. Of a sound or voice, to make or become lower in pitch.^[2][9]

Word family

• deepener
• deepeningly
• overdeepen

Related words

• deep
• depth
• dip

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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ 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)
8. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
9. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
10. ^ a b c Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
11. ^ 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)
12. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins