Etymologically
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litmus

This is the current revision of this entry, as edited by bogdan on 14 October 2026 at 16:58. This address is a permanent link to this version.
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Pronunciation

  • IPA: /ˈlɪtməs/[1]

Etymology

It comes from Middle English litmose,[2][3][4] of Scandinavian origin;[2][5][6][3] compare Old Norse litmosi (“herbs used in dyeing”),[2][3][4] from litr “color, dye”[2][6][3][4] and mosi “moss”.[2][5][6][3][4] Barnhart and Etymonline say the word is also partly from Middle Dutch lijkmoes or lēcmoes,[5][6] whose first element Barnhart connects with leak.[5] It is related to moss.[6][3]

Earliest recorded meaning

A blue coloring matter obtained from lichens (1320 as lykemose and 1324–25 as litemose in Barnhart, but 1502 in the OED).[5][7]

Semantic evolution

The dye is naturally blue, turns red in acid and becomes blue again in alkali,[6][4] and so came to be used as a chemical indicator.[4] Litmus paper, treated with the dye, is recorded from 1803.[5][6] From its use in chemistry came the figurative litmus test, a single decisive test, from 1957.[5][6]

Timeline

  • 1320 – lykemose (Barnhart).[5]
  • 1324–25 – litemose (Barnhart).[5]
  • 1495–1505 – Random House's dating.[4]
  • 1803 – litmus paper.[5][6]
  • 1957 – litmus test, figurative.[5][6]

Modern meaning

Noun

  1. A blue powder obtained from certain lichens, which turns red in acid solutions and blue in alkaline ones, used as an indicator.
  2. A litmus test; the deciding factor in such a test.

Word family

  • litmus paper
  • litmus test
  • moss
  • lichen
  • leak

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin
  3. ^ a b c d e f Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
  4. ^ a b c d e f g Random House Webster's Unabridged Dictionary (1999), 2nd ed., New York: Random House
  5. ^ a b c d e f g h i j k Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
  6. ^ a b c d e f g h i j Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  7. ^ Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press