'overzealousness' originates from the English word 'zealous,' which comes from the Medieval Latin word 'zelosus,' where 'zelosus' meant 'full of zeal.'

'zealous' changed from the Medieval Latin word 'zelosus' and eventually became the modern English word 'zealous.'

Initially, it meant 'full of zeal or fervor,' and this meaning has largely remained the same in modern usage.