'backorder' originates from English, specifically the components 'back' (from Old English 'bæc') and 'order' (from Old French 'ordre', from Latin 'ordo'), where 'back' meant 'behind' or 'at the back' and 'order' meant 'a request or instruction to supply.'

'backorder' was formed as a compound in modern English (particularly in 20th-century commercial usage) combining 'back' + 'order' and eventually became the standard business term 'backorder'.

Initially it referred broadly to an order that was held back or delayed; over time it specialized to mean 'an order for goods not currently in stock that will be delivered when available.'