From Latin 'expendere' (to weigh out) — preserving the ancient practice of paying by weighing metal. 'Spend' is its eroded twin.
To spend or use up a resource, especially money, energy, or time.
From Latin 'expendere' (to weigh out, pay out), composed of 'ex-' (out) and 'pendere' (to weigh, to pay). In ancient Rome, payment was made by weighing out metal — coins and bullion were suspended from a balance and measured by weight. To 'expendere' was to weigh out money, to pay by suspending metal on a scale. The word captures the
English 'spend' is just a shortened form of 'expend.' Old French clipped Latin 'expendere' down to 'despendre' and then 'espendre,' which English borrowed and simplified to 'spend.' So 'spend' and 'expend' are the same word at different stages of phonetic erosion — one compressed by centuries of French and English mouths, the other preserved in its fuller Latin form.