back ‧ log /ˈbæklɒɡ $ -lɒːɡ, -lɑːɡ/ BrE AmE noun [countable usually singular]
[ Date: 1900-2000 ; Origin: backlog 'large piece of wood placed at the back of a fire' (17-21 centuries) ]
a large amount of work that you need to complete, especially work that should already have been completed
backlog of
a backlog of requests
It’s going to take us months to clear the backlog.