'unwearied' originates from Middle English, specifically the prefix 'un-' meaning 'not' and the word 'wearied,' where 'wearied' meant 'tired or fatigued.'

'unwearied' changed from the Middle English word 'unweried' and eventually became the modern English word 'unwearied'.

Initially, it meant 'not tired or fatigued,' and this meaning has largely remained the same in modern usage.