'backorder' originates from the combination of 'back' and 'order', where 'back' refers to a delay or backlog, and 'order' refers to a request for goods.

'backorder' evolved from the practice of recording orders that could not be immediately fulfilled, eventually becoming the modern term 'backorder'.

Initially, it referred to any order placed for future delivery, but now it specifically refers to orders delayed due to stock unavailability.