Part one of term paper
The term firewall has seen limited use since the late 1980s to describe a device to block unwanted network traffic while allowing other traffic to pass. The first published description of a "modern" firewall including use of that name was in 'Practical Unix Security' written in 1990 and published in 1991. The first description of a firewall, ...

Part two of term paper
... to a security device was by Steve Bellovin, in some email to Phil Karn, in 1987. But the context suggests that Phil knew what Steve meant, yet Steve doesn't think he invented it. What is a network firewall? A firewall is a system or group of systems that enforces an access control policy between two networks. The actual means by which this is accomplished varies widely, but in principle, the firewall can be thought of as a pair of mechanisms: one that exists to block traffic, and the other that ...