Firewall

wiktionary

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From fire +‎ wall. Compare West Frisian brânmuorre, Dutch brandmuur, German Brandmauer, Feuermauer, Swedish brandvägg, brandmur, Icelandic eldvegg.

etymonline

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firewall (n.)

also fire-wall, 1851 as a physical wall meant to prevent the spread of fire in a structure, from fire (n.) + wall (n.). Computer sense (originally figurative) is by 1990.