'Spend' is Latin for 'weigh out' — from 'pendere' (to weigh). Paying by weight on a scale.
To pay out money in buying or hiring goods or services; to use up or devote time, energy, or effort to a particular activity or purpose.
From Old English 'spendan' (to spend, to expend), borrowed early from Latin 'expendere' (to weigh out, to pay out), a compound of 'ex-' (out) + 'pendere' (to weigh, to hang, to pay). The Latin verb reflects the ancient practice of paying by weighing out metal: before coinage was standardized, payments were made by weighing silver or gold on scales. To spend is etymologically to 'weigh out' — to measure and surrender your metal
Spend comes from Latin 'pendere' (to weigh), because before coins existed, you paid by weighing metal on a scale. The same root gives 'pension' (a payment weighed out regularly), 'compensate' (to weigh together, to balance), 'suspend' (to hang under), and 'pendant' (something that hangs). The British 'pound' sterling was originally a pound weight of silver