"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 675][1], 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][2]", 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 793][3], 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.


  [1]: https://tools.ietf.org/html/rfc675
  [2]: https://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf
  [3]: https://tools.ietf.org/html/rfc793