thickness

Etymology

It is inherited from Middle English thiknesse,^[2][3][4] inherited from Old English þicnes (“density; depth; thicket”),^[2][5][6] formed from Old English þicce + -nes, that is from the adjective thick and the suffix -ness.^[3][5][7] The OED compares Old High German diknissa.^[5]

Earliest recorded meaning

In Old English the noun meant density or viscosity, hardness, and depth as opposed to length or breadth, and also anything thick or heavy, darkness, or a thicket.^[2] The OED's earliest Old English uses include bulk, the third dimension of an object, the consistency of a liquid, and haze or darkness of the air.^[5]

Semantic evolution

Most of the senses were already present in Old English.^[5][2] Stoutness of the body is recorded from the late 14th century,^[2] and the closeness of things growing or crowded together from 1398, in Trevisa.^[5] A sense of indistinct speech or dull hearing is recorded from 1538.^[5] Johnson (1755) defined it as density, the quantity of matter interposed, and a layer laid on another.^[8] The concrete sense, a layer of cloth, paper or the like, is dated from 1815,^[5] and a back-formed verb, to plane boards to an even thickness, from 1978.^[5][3]

Timeline

• Old English – density; depth; bulk; a thick part.^[5][2]
• late 14th century – stoutness of body.^[2]
• 1398 – closeness, crowdedness.^[5]
• 1538 – indistinctness of speech or hearing.^[5]
• 1815 – a layer.^[5]
• 1978 – the verb, to plane to an even thickness.^[5]

Modern meaning

Noun

1. The state or quality of being thick.
2. The distance through an object, as distinct from its length and width: The ice was only a few centimetres in thickness.
3. The density or viscosity of a liquid, smoke, hair or the like.
4. A layer of something: three thicknesses of cardboard.

Verb

1. To make boards or planks of a uniform thickness.

Related words

• thick
• thicken
• thicket

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ a b c d e f g h i j k l m n Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
6. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
7. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.