A secondary path or minor walkway, not the main route.
Compound of 'by-' (meaning secondary or incidental) and 'walk' (Old English 'wealcan'). The term refers to paths that exist alongside or as alternatives to main thoroughfares.
Medieval towns were designed with main streets and 'bywalks'—the hidden pathways that local people used to cut through town. These forgotten routes are why many old European towns still have mysterious alleyways that don't seem to go anywhere!
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