sidewalk

This word is simply a compound of side and walk, joined to name the path alongside a road. Side traces back through Old and Middle English to Proto-Germanic sīdǭ and sīdaz, ultimately from Proto-Indo-European seh₁-der.

The compound came together in English by fusing two already-existing words, side and walk, to describe a specific kind of path — the walk that runs along the side of something.

It shares its first half with every other English word built on side, tracing back to the same Proto-Germanic and Proto-Indo-European roots.