The DoD created the Internet Protocol stack (TCP/IP is slang for IP Stack).
This was a decade before the OSI model was created.

However, the seven layers of the OSI match up well with the four layers of the DoD model. The OSI just broke the layers into smaller sections, which made sense since we were using many, many different protocols and the DoD model was created to use the IP stack only.

The Host to Host layer of the DoD model provides the same functionalilty as the Transport layer of the OSI model, so Cisco uses those terms interchangabily. Same as with the Network layer of the OSI and the Internet layer of the DoD.

With that said, I do not make this stuff up. I write the questions based on the objectives of the CCNA and Cisco can use either term to refer to the functions of a layer. Transport = Host to Host, Network = Internet. Why? Because do you use any other protocols besides IP today? no.

Todd Lammle