Firewall

Part of speech: noun

Pronunciation: /ˈfaɪə.wɔəl/

Definitions

1. A protective barrier in a computer network that blocks unauthorized access while allowing authorized communication
2. A security measure designed to prevent unwanted or harmful network traffic from entering or exiting a computer system
3. A software or hardware solution that controls incoming and outgoing network traffic based on predetermined security rules

Etymology: A firewall was originally a literal wall. Its name comes from the building trade, where a "firewall" is a fire-resistant wall built inside or between structures to stop a blaze from spreading from one section to the next. The computing sense is a metaphor drawn from that architectural idea: a barrier placed between a protected network and outside traffic, blocking whatever threatens to cross over. The compound is simply "fire" plus "wall," and the same pairing appears across Europe. German speakers have "Brandmauer" and "Feuermauer," Dutch has "brandmuur," and Swedish has "brandvägg," all built from the same elements. Iceland's "eldvegg" follows the same pattern, showing how independently European languages reached for the same image of a wall that holds back flames.

Synonyms: security barrier, protective barrier, defensive wall, safety net, screen