'halfheartedly' originates from the English word 'halfhearted', where 'half' meant 'partially' and 'hearted' referred to 'having heart or enthusiasm'.

'halfhearted' evolved from the Middle English word 'halfherte', which combined 'half' and 'herte' (heart), eventually becoming the modern English word 'halfhearted'.

Initially, it meant 'having only part of one's heart or enthusiasm', and this meaning has largely remained the same in modern usage.