'backlog' originates from the combination of 'back' and 'log', where 'back' refers to the rear or past, and 'log' refers to a record or list.

'backlog' was initially used to describe a large log placed at the back of a fire to keep it burning, and eventually became a metaphor for tasks waiting to be completed.

Initially, it meant 'a large log for a fire', but over time it evolved into its current meaning of 'an accumulation of tasks'.