thicken

Etymology

It is inherited from Middle English thikken, also thiknen,^[2][3][4] formed from English thick + -en.^[5][4][6][7] The Middle English Dictionary derives it from the adjective and compares Old English þiccian (“to thicken, crowd together”),^[2][4] and Etymonline treats that as an earlier verb, thick.^[4] The OED compares Old Norse þykkna,^[5] which Dictionary.com gives as the direct source.^[8] Thick is from Old English þicce, from Proto-Germanic *þekuz.^[5][1]

Earliest recorded meaning

To become more viscous or to make a liquid so: the Middle English Dictionary, which includes forms without -en, begins with hit þickez of about 1300, and has milk of almonds iþikked with starch before 1325.^[2] Etymonline dates thikkenen to the late 14th century,^[4] and the OED's first record is about 1425, in a translation of Arderne's treatises on fistula.^[5]

Semantic evolution

The word spread from the consistency of liquids to other kinds of density: the Middle English Dictionary already records building up a wall by adding depth, making cloth fuller, moving in a crowd and increasing in frequency.^[2] Etymonline and the OED date the intransitive "become thicker" to the 1590s,^[4][5] and Shakespeare's Macbeth has the sense of growing dark.^[5] Othello has the figurative "make more substantial, confirm",^[5][9] and Johnson (1755) quoted it under "to strengthen, to confirm".^[9] The OED's first record for growing more complex, especially of a plot, is in the Duke of Buckingham's Rehearsal (1672).^[5] The sense "fill up the gaps" is treated as obsolete by the Shorter Oxford, while Merriam-Webster still lists it.^[7][3] Middle English also had thikkeren, to make milk more viscous, from thicker, in the late 15th century.^[4]

Timeline

• c. 1300 – to become more viscous.^[2]
• c. 1425 – transitive, to make dense in consistency, to coagulate.^[5]
• c. 1578 – to make close or dense in arrangement.^[5]
• 1598 – intransitive, to increase in density.^[5] Etymonline dates it to the 1590s.^[4]
• c. 1611 – to make thicker in measure.^[5]
• before 1616 – to grow dark, misty; figuratively, to confirm or strengthen.^[5]
• 1672 – to become more complex, especially of a plot.^[5]
• 1726 – to become crowded or numerous.^[5]
• 1763 – to grow in girth or bulk.^[5]

Meanings

Verb

1. To make denser or more viscous: He thickened the stew with cornflour.^[10][3][5]
2. To become denser or more viscous: The sauce thickens as it cools.^[10][5]
3. To become darker or more opaque; of the weather, to turn misty.^[5][7]
4. To make or become greater in measurement or girth.^[3][5][7]
5. To grow crowded, numerous or frequent.^[5][9]
6. Of a plot, to become more complex: the plot thickens.^[10][5][7]
7. To make more substantial; to strengthen or confirm.^[3][5][7]
8. To make close or compact; to fill up the gaps in.^[3][5]

Word family

• thickener
• rethicken
• unthicken

Related words

• thick
• thicket
• thickness

Usage notes

Green's Dictionary of Slang records a separate noun thicken, a sovereign, in 1886, perhaps from thick 'un.^[11]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e 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)
3. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ 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
6. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
7. ^ a b c d e f Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
9. ^ 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.
10. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
11. ^ Green, Jonathon (2010), Green's Dictionary of Slang, London: Chambers; digital ed. 2016–, https://greensdictofslang.com