The term is most common in telecommunications, where an order for a new line or circuit passes through sales, credit, serviceability checks, provisioning and activation. Missing site details, a failed number port or a mismatch between the quote and the product catalog can all stop it partway, and someone has to find out why.
Fallout costs time twice: once to diagnose the problem and again in the delayed activation the customer notices. The most effective fix is usually upstream, validating orders for completeness before they leave sales, then routing what still falls out to the right team with the context already gathered.