'backlog' originates from English, specifically the compound 'back' + 'log', where 'back' meant 'rear' and 'log' meant 'a piece of wood or a record'.

'backlog' originally referred to a literal 'log placed at the back (of a fire)' and was later used figuratively (18th–19th century) to denote stored items or reserves; by commerce and administration it developed the modern sense of 'an accumulation of uncompleted work or pending orders'.

Initially, it meant 'a log placed at the back (or a reserve)', but over time it evolved into its current meaning of 'an accumulation of uncompleted work or pending orders'.