"Transport" in place of "Transmission" just looks like a mistake.
However, in some early documents "TCP" is used to mean "Transmission Control Program" not "Protocol", as you can see in RFC 675RFC 675, written by Cerf et al and dated December 1974.
Both earlier and current documents use "Transmission" uniquely:
- "Protocol" is used in Cerf and Kahn's slightly earlier landmark paper "A protocol for packet network intercommunication", published May 1974 in (IEEE Transactions on Communication, vol. C- 2O, No. 5. May 1974, pp. 637-648.)
- The standard as we now know it, RFC 793RFC 793, uses "Protocol". This was published in 1981 and it is only attributed to the "Information Sciences Institute", though editor Postel describes it as having many authors.