firewall

Etymology

It is a compound from English fire + wall.^[2][3] It is also spelled with a hyphen.^[3]

Earliest recorded meaning

An unbroken line of flames forming a barrier, a wall of fire: 1578, in W. Hilton's translation of a sermon by Urbanus Regius, a sense the OED calls somewhat rare.^[2]

Semantic evolution

The sense of a wall built to stop the spread of fire, especially one in a building that rises above the roof, is recorded from about 1666.^[2] Etymonline dates this sense to 1851,^[3] and Dictionary.com dates the word to 1750–60 and labels it an Americanism.^[4] From 1907 the word was used figuratively for anything that protects a system or institution as a barrier.^[2] In computing it came to mean hardware or software that blocks unauthorized access to or from a network: the OED's first record is from 1971,^[2] while Etymonline dates the computer sense, originally figurative, to 1990 at the latest.^[3] The verb followed: in aviation, to push a throttle fully open, towards the firewall between cockpit and engine (1958); in computing, to protect with a firewall (1984); and generally, to keep something separate or isolated (1999).^[2]

Timeline

• 1578 – a wall of flames.^[2]
• c. 1666 – a wall built to stop the spread of fire.^[2] Etymonline dates this sense to 1851.^[3]
• 1907 – figuratively, a protective barrier around a system or institution.^[2]
• 1958 – verb, to open a throttle fully.^[2]
• 1971 – in computing, a system protecting a network from unauthorized access.^[2] Etymonline dates the sense to 1990 at the latest.^[3]
• 1984 – verb, to protect with a firewall.^[2]
• 1999 – verb, to keep separate or isolated.^[2]

Meanings

Noun

1. A fireproof wall or partition built to stop a fire spreading from one part of a building, vehicle or aircraft to another.^[5][6][2]
2. (computing) A program or device that protects a computer or private network against unauthorized access from outside, as from the Internet.^[5][6][2]
3. (figurative) A barrier or safeguard that keeps something separate or protected.^[2]

Verb

1. (computing) To protect a computer or network with a firewall.^[6][2]
2. To keep something separate or isolate it.^[2]
3. (aeronautics) To open a throttle fully.^[2]

Related words

• fire
• wall

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r s Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f 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 Collins English Dictionary (2023), Glasgow: HarperCollins
6. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt