insulator

Etymology

It is formed from English insulate + -or, as an agent noun in Latin form.^[2][3][4] The verb is from Latin īnsula (“island”),^[2][5][3] the source of isle.^[3][5]

Earliest recorded meaning

Something that entirely or largely stops the passage of electricity or heat between adjoining bodies: 1801, in the Supplement to the Encyclopædia Britannica.^[2][3][5]

Semantic evolution

The word took its meaning from the verb, whose sense of blocking electricity or heat Etymonline dates from 1742, after the first sense "to make into an island".^[3] Etymonline also dates its use for the glass or earthenware fittings that hold telegraph wires, and later telephone wires, to the 1840s.^[3] Merriam-Webster Unabridged also has it for a worker who applies electrical or thermal insulation.^[5]

Timeline

• 1801 – a body or substance that stops the passage of electricity or heat.^[2][3][5]
• 1840s – a glass or earthenware device that holds telegraph wires.^[3]

Meanings

Noun

1. A material or body that conducts electricity, heat or sound very poorly.^[6][5][7]
2. A device of such material that supports a conductor or keeps it from contact with others or from earth.^[5][7]
3. A worker who applies electrical or thermal insulation.^[5][8]

Related words

• insulant
• insulate
• insulation
• isle

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
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 Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
7. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
8. ^ Gove, Philip Babcock, ed. (1961), Webster's Third New International Dictionary of the English Language, Unabridged, Springfield, Mass.: G. & C. Merriam