'money-waster' originates from Modern English, formed by combining the noun 'money' + the verb 'waste' with the agentive suffix '-er' to indicate someone or something that causes money to be wasted.

'money' comes from Old French 'moneie' (from Latin 'moneta'); 'waste' comes from Old North French/Old French 'waste/gaster' (from Germanic roots meaning 'desert' or 'ruin'); the agentive suffix '-er' is from Old English/Germanic usage for doer/agent. These elements combined in Modern English to form the compound 'money-waster'.

Initially the separate elements referred to 'money' and 'waste' in their original senses; over time the compound came to be used as a straightforward label for a person or thing that wastes money.