abstruse

Etymology

It is borrowed from Latin abstrūsus (“concealed, hidden, secret”),^[2][3][4] the past participle of abstrūdō (“to conceal”),^[2][3][5] literally "to thrust away",^[6][7] formed from abs- (“away”), a variant of ab-, and trūdō (“to thrust, push”),^[5][3] from Proto-Indo-European *treud- (“to press, push, squeeze”).^[6][8][9] Barnhart, Hoad, Etymonline, Ayto and the Shorter Oxford leave open a route through Middle French abstrus,^{[5][10][6][7][11]} while the OED and Merriam-Webster take the word directly from Latin; the OED only compares French abstruse (1531), Catalan abstrús (1696), Italian astruso (1623) and Spanish abstruso (1726).^[2][3] Klein compares Old English þrēatian (“to press, afflict, threaten”).^[8]

Earliest recorded meaning

Difficult to understand, obscure: about 1549, in J. Hooper's declaration of the Ten Commandments, in the OED's revised entry;^[2] Merriam-Webster also has about 1549.^[3] Barnhart dates the word to 1599 and Etymonline to the 1590s.^[5][6]

Semantic evolution

Ayto takes "concealed" as the original, literal meaning and notes that the metaphorical "obscure" is just as old in English;^[7] in the OED's record "obscure" comes first and "concealed, secret" follows in 1576.^[2] The literal sense lasted until the 18th century: Milton's Paradise Lost speaks of "abstrusest thoughts" hidden from everything but the eternal eye,^[12][3] and Johnson (1755) still listed "hidden" first and "difficult, remote from conception or apprehension" second.^[12] In 1656 P. Heylyn put the word among the "uncouth and unusual" terms in H. L'Estrange's Reign of King Charles, although, as the OED notes, it was well attested by then.^[2]

Timeline

• c. 1549 – difficult to understand, obscure.^[2][3] Barnhart has 1599.^[5]
• 1576 – concealed, hidden, secret (obsolete by 1759).^[2]
• early 17th century – the adverb abstrusely.^[11]
• mid 17th century – the noun abstruseness.^[11]

Meanings

Adjective

1. Hard to understand; recondite or esoteric: an abstruse legal argument.^[13][3][2]
2. Concealed, hidden, secret (obsolete, 1576–1759).^[2][3][11]

Word family

• abstrusely
• abstruseness
• abstrusity

Related words

• abstrude
• threat
• intrude
• extrude
• obtuse

Usage notes

Dictionary.com lists abstruse as a word that can be confused with obtuse.^[14]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h i Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
5. ^ a b c d e Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
6. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b c Ayto, John (2005), Word Origins: The Secret Histories of English Words from A to Z, 2nd ed., London: A & C Black
8. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
9. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
10. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
11. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
12. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
13. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
14. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House