means A solid upright structure, usually of brick, stone, or timber, that encloses a space, divides an area, or supports a roof.

from From Old English 'weall,' a barrier or rampart — but the deeper root is borrowed Latin 'vallum,' the earthwork wall the Romans threw up around their camps, itself from 'vallus,' a stake or palisade. So every wall traces back to a row of pointed sticks hammered into the ground by soldiers.