intruder

Etymology

It is formed from English intrude + -er.^[2][3][4] Intrude is from Latin intrūdō (“to thrust in, force in”),^[2][3][5][6] formed from in- (“in”) and trūdō (“to thrust, push”),^[2][5][7] from Proto-Indo-European *treud- (“to press, push, squeeze”), the root of threat.^[3][5][7] Etymonline suggests the verb may instead be a back-formation from intrusion.^[3] The OED compares Middle French intruire (1479) and its past participle intrus.^[2] Klein compares Gothic 𐌿𐍃𐌸𐍂𐌹𐌿𐍄𐌰𐌽 (usþriutan, “to vex”) and Old English þrēotan (“to weary, vex”).^[7]

Earliest recorded meaning

A legal term, one who intrudes into an estate or benefice or takes over the rights of another: 1534, in an Act of Henry VIII.^[2][3]

Semantic evolution

The word began in law:^[3] an intruder was one who entered on an estate, especially after a life tenancy had ended and before the heir had taken possession, without any right to it.^[2] The general sense, one who pushes in where not invited or welcome, appears in Shakespeare's Titus Andronicus (1594),^[2] and Johnson (1755) defined it as one who forces himself into company or affairs without right or welcome.^[4] Thomas Fuller used a feminine intrudress in 1650.^[3] In the Second World War the word was used of an aircraft, or its pilot, sent over enemy airfields to disrupt operations (1941).^[2][6] Today it most often means someone who enters a building or grounds without permission.^[8]

Timeline

• 1534 – law, one who intrudes into an estate or benefice.^[2][3]
• 1594 – one who thrusts in uninvited.^[2]
• 1650 – the feminine intrudress, in Fuller.^[3]
• 1941 – an aircraft sent to attack enemy airfields.^[2]

Meanings

Noun

1. A person who enters a building or grounds without permission, especially to commit a crime: The alarm scared off the intruder.^[8][6]
2. Anyone or anything that intrudes, coming in where not invited or welcome.^[6][2][4]
3. A military aircraft sent alone into enemy territory, usually at night, to attack its airfields.^[6][2]
4. (law) One who enters on an estate without right, especially after a life tenancy has ended.^[2]

Related words

• intrude
• intrusion
• intrusive
• threat
• thrust
• abstruse
• extrude
• obtrude
• protrude

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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h i Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ 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.
5. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
6. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
8. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins