'weak-willed' originates from the combination of 'weak' and 'will,' where 'weak' meant 'lacking strength' and 'will' referred to 'the faculty by which a person decides on and initiates action.'

'weak-willed' evolved from the Old English word 'wac' (weak) and 'willan' (to wish or desire), eventually forming the modern English term 'weak-willed.'

Initially, it meant 'lacking strength in decision-making,' and this meaning has largely remained the same in modern usage.