The word 'staunch' has a journey from a concrete physical action to a more abstract quality of character. Its ultimate origin is the Latin verb 'stāre', meaning 'to stand', a concept of stability and firmness. Through Vulgar Latin and Old French, it evolved into a verb specifically for making something stand still, such as stopping the flow of blood from a wound. This core idea of stopping a flow or leak gave rise to the adjectival sense describing something watertight or strong in construction, and later, by metaphorical extension, to a person who is firm, dependable, and loyal in their support, effectively 'stemming the tide' of opposition or difficulty.

This word is a simplex form. It entered Middle English from the Old French word 'estanchier', meaning 'to stop the flow of (blood)'. The Old French term likely derived from the Vulgar Latin 'stanticāre', which is related to the Latin 'stāre', meaning 'to stand'.