When was the first time the word “Macedonia” was defined to include lands of the nowadays Rep. of Skopje?

After the Russo-Turkish war of 1877-1878 which ended with a Russian victory the two parties signed what became known as the treaty of San Stefano (1878).
The chief Russian negotiator was Count Ignatiev, the Panslavist Russian Ambassador at Constantinople between 1864-1877. The statistics used by Ignatiev during these negotiations, when he gave a new definition to the word “Macedonia”, were provided to him by a Bosnian, Kerkovic. The San Stedano treaty provided for the creation of “Greater Bulgaria” that would include the then Bulgarian state, Eastern Rumelia, parts of today’s Albania as far to the west as the city of Koritsa, and “Macedonia” which was then first defined to include what is known nowadays as Republic of Skopje, the southwestern part of nowadays.
Bulgaria, and Macedonia (of Greece). It is interesting to note that the three Turkish vilaets covering this “Macedonia” were the vilaets of Thessaloniki, Monastirio and parts of the vilaet of Kossovo. The city of Skopje was in the vilaet of Kossovo.
Even the most extremist Bulgarian nationalists celebrated on the good news. The other European powers objected to this settlement because they feared that it would give Russia the ability to seize easily Constantinople. One of these powers, Austria-Hungary, was displeased by the prospect of Bulgaria holding the port of Thessaloniki as this would have barred its own descent to this port through Bosnia.
In the Berlin Congress, held weeks later, in the summer of 1878, the arrangements of the San Stefan Treaty (regarding Bulgaria) were cancelled with the full agreement of Russia since Russia did not want to risk a war against the other European Powers.
The “Macedonia” of the San Stefano treaty thus remained under Ottoman rule divided into various vilaets and sandjaks. It is ironic that this new definition of “Macedonia”, invented for the purpose of delivering lands of the Ottoman empire to Bulgaria on the occasion of the San Stefano Treaty, outlived that Treaty and is still used by some people to define Macedonia.
The end result of the San Stefano treaty was that it gave Bulgaria the pretext to actively interfere in “Macedonia”, as it would become apparent from later events in the region.