'well-founded' originates from the combination of 'well,' meaning 'in a good or satisfactory way,' and 'founded,' which comes from the Old French 'fonder,' meaning 'to establish or base.'

'founded' changed from the Old French word 'fonder' and eventually became the modern English word 'founded.'

Initially, 'founded' meant 'to establish or base something,' and this meaning has largely remained the same in modern usage.