insulate

Etymology

The American Heritage Dictionary, Merriam-Webster and the Oxford Dictionary of English take it as formed from Latin īnsula (“island”) with the English suffix -ate,^[2][3][4] while Etymonline, Collins, Dictionary.com and Klein derive it from īnsulātus (“made into an island”).^[5][6][7][8] The OED and the Shorter Oxford leave both open,^[9][10] and the OED notes that a verb *īnsulāre is not recorded in late or medieval Latin, though it may have existed.^[9] Barnhart calls the formation uncertain: probably at first from the noun, later from the adjective, with some later uses perhaps a back-formation from insulation.^[11] Isolate is a doublet,^[11][8] and the OED compares Italian isolare, known in the 16th century.^[9] The origin of the Latin noun is itself uncertain:^[5][11] the ancient guess in salō (“in the salty sea”) is according to de Vaan only theoretically possible, and it may be a loan from an unknown language.^[5]

Earliest recorded meaning

To make land into an island: Barnhart dates this to 1538 and Etymonline to the 1530s,^[11][5] and Dictionary.com gives 1530–40.^[7] The OED's first record is from before 1552, in Leland's Itinerary.^[9]

Semantic evolution

The word first described geography,^[9] and the Shorter Oxford and Merriam-Webster now mark that use as archaic.^[10][3] An adjective insulate, detached or isolated, followed in 1712,^[9][11] and insulated, isolated, in 1727.^[11] The electrical sense came in 1742, in Desaguliers, for cutting a body off from conductors,^[9][11][5] earlier than the general verbal sense of setting something apart, which the OED and Etymonline date to 1785.^[9][5] The Shorter Oxford, however, puts that general sense in the early 18th century.^[10] This use also covers heat and sound,^[9][11] and between 1830 and 1834 chemists and physicists also used the verb for freeing a substance from combination with other elements, as Herschel did.^[9] The nouns insulation (1767) and insulator (1801) followed.^[11]

Timeline

• 1538 – to make land into an island.^[11] The OED's first record is from before 1552.^[9]
• 1712 – adjective, detached, isolated.^[9][11]
• 1727 – the participle insulated, isolated.^[11]
• 1742 – to separate from conducting bodies.^[9][11][5]
• 1767 – the noun insulation.^[11]
• 1785 – to set apart from surroundings.^[9][5]
• 1801 – the noun insulator.^[11]
• 1830 – to free from combination with other elements (obsolete by 1834).^[9]

Meanings

Verb

1. To stop the passage of heat, electricity or sound into or out of something, usually by covering it with non-conducting material: We insulated the water pipes before the first frost.^[2][4][6][3]
2. To set apart or isolate; to shield from outside influences: Her savings insulated the family from the recession.^[2][6][3][9]
3. (archaic) To make land into an island.^[3][10][9]

Adjective

1. (rare) Set apart, detached.^[10][3][9]

Word family

• insulative
• reinsulate
• insulator
• insulation

Related words

• insular
• isolation
• peninsula
• isle
• isolate
• insulin

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
3. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
5. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
7. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
9. ^ a b c d e f g h i j k l m n o p q r Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
10. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
11. ^ a b c d e f g h i j k l m n o Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology