Other forms: scaffolds
A scaffold is a framework for builders — or, in an older sense, the raised platform used for executions. The same word, two very different structures.
The building sense is the living one, and a single structure is a scaffold while the whole system of poles and boards is scaffolding. The execution sense survives in history writing, and going to the scaffold is a fixed phrase. Teaching borrowed the word for temporary support given to learners. Biology has scaffolds too, meaning structures that cells are grown on.
A scaffold was a grandstand. Old French escadafaut named a platform for watching a tournament, from a Latin word for a viewing stage, so the builders' frame and the executioner's platform both begin as somewhere to stand and watch.
Ancient Greek
κατα- — back; against
Vulgar Latin
*catafalcum — viewing stage
Latin
ex- — out, away
Old French
es-
Anglo-Norman
schaffaut
Middle English
scaffold
English, today
scaffold
Built from
From Middle English scaffold, scaffalde, from Anglo-Norman schaffaut, eschaffaut, eschafal, eschaiphal, escadafaut (“platform to see a tournament”) (Modern French échafaud), from Old French es- (from Latin ex- (“out, away”)) + chafaud, chafaut, chafault, caafau, caafaus, cadefaut (“scaffold for executing a criminal”), from Vulgar Latin catafalcum (“viewing stage”), possibly from Ancient Greek κατα- (“back; against”) + Latin -falicum (from fala, phala (“wooden gallery or tower; siege tower”)).
Etymology from Wiktionary, CC BY-SA