'lightheartedly' originates from the combination of 'light' and 'hearted,' where 'light' meant 'not heavy' and 'hearted' referred to 'spirit or mood.'

'lighthearted' transformed from the Old English word 'leohtheort,' which meant 'light in spirit,' and eventually became the modern English word 'lighthearted.'

Initially, it meant 'light in spirit or mood,' and this meaning has largely remained the same in modern usage.