Origins
The word 'wall' is, like 'street,' a Latin loanword of great antiquity in the Germanic languages — borrowed not through books or through French, but through direct contact between Germanic peoples and Roman military architecture. It is a word born on the frontier, where two civilizations met and one built structures the other had no name for.
Old English 'weall' could mean a wall, a rampart, a cliff, or a defensive fortification. It descends from a Proto-West Germanic borrowing '*wallu,' taken from Latin 'vallum.' In classical Latin, 'vallum' had a specific meaning: a defensive earthwork or rampart, typically consisting of an earth embankment topped with a palisade of wooden stakes ('valli,' plural of 'vallus,' meaning 'stake'). A 'vallum' was not a freestanding wall of stone but rather a military fortification made of earth and timber.
The borrowing almost certainly occurred in the context of Roman frontier defenses. Germanic peoples encountered Roman fortifications along the Rhine, the Danube, and in Britain, where Hadrian's Wall — the most famous Roman frontier structure — was accompanied by a parallel earthwork that Roman sources literally called the 'Vallum.' The Germanic adoption of 'vallum' to describe these imposing defensive structures, and then by extension any large wall, is a sign of the impression Roman military engineering made on the peoples beyond the frontier.
Old English Period
The word appears in all the West Germanic languages: German 'Wall' (still meaning specifically a rampart or embankment, as distinct from 'Wand' or 'Mauer' for other types of wall), Dutch 'wal' (embankment), and the Scandinavian forms Swedish 'vall' (embankment) and Norwegian 'voll.' The semantic range varies instructively: German preserves the original military sense most closely, while English generalized 'wall' to mean any vertical enclosing structure, eventually displacing the native Old English words for wall and partition.
The Latin source word 'vallus' (stake) may be connected to PIE '*walso-' (a post), though this etymology is not universally accepted. More confidently, 'vallum' is the source of the English word 'interval,' which comes from Latin 'intervallum,' literally 'the space between rampart stakes' — the gap between the palisade posts. The fact that 'interval' preserves the original military sense of 'vallum' more faithfully than 'wall' does is a nice irony.
In Old English poetry, 'weall' frequently carries a sense of grandeur and permanence that reflects the awe Anglo-Saxon settlers felt at Roman ruins. The Old English poem 'The Ruin,' which describes a crumbling Roman city (probably Bath), uses 'weall' repeatedly to evoke the massive stone structures the Anglo-Saxons found already ancient when they arrived in Britain. The compound 'weallstān' (wall-stone, ashlar) and the poetic epithet 'ealdweall' (old wall) appear in descriptions of Roman remains that the Anglo-Saxons could not replicate with their own building technology.
Figurative Development
The metaphorical uses of 'wall' are extensive and deeply embedded in English. 'Wall Street' (named for a literal defensive wall in 17th-century New Amsterdam) has become the global metonym for finance. The 'Berlin Wall' became the defining symbol of Cold War division. 'To go to the wall' means to be ruined or defeated. 'Off the wall' means unconventional. 'The writing on the wall,' from the biblical Book of Daniel, means an ominous warning. In each case, the metaphor draws on the wall's fundamental function as a barrier — something that separates, encloses, or excludes.
The technological history of walls is inseparable from the history of civilization itself. The walls of Jericho, dating to approximately 8000 BCE, are among the oldest known structures. City walls defined the boundary between civilization and wilderness in the ancient world, and the construction of walls — from Hadrian's Wall to the Great Wall of China to modern border barriers — remains one of humanity's most powerful and contested political acts. That the English word for this fundamental structure should itself be an artifact of Roman-Germanic frontier contact gives it a reflexive quality: 'wall' names a boundary, and the word itself was born on one.