I chanced upon a place in one of John Wesley's sermons where he used the word "evangelical." I've been curious about how the word was used prior to the twentieth century. I've generally found that those who argue for continuity of a concept throughout history (e.g., Al Mohler's sense of inerrancy throughout history) generally have a rather superficial understanding of how meaning works.
Just because someone uses the same or a similar word in a different time and place doesn't at all mean that they used the word in the same way. Meaning is always culturally embedded. The "denotation" of certain words may even seem the same, but the "connotations" may be quite different.
Thus is my contention that to be "evangelical" in the twentieth century is not the same thing as calling something "evangelical" in another time and place. The most obvious example here is the fact that "evangelisch" in German simply means Protestant and has little to do with being evangelical in the US today.
In any case, Wesley uses the word "evangelical" three times in his sermon, "The Spirit of Bondage and Adoption." He is sketching out stages in a person's spiritual development. He sees three: 1) the natural state, 2) the legal state, and 3) the evangelical state (IV.1).
The progression goes something like the following. The natural state is not really aware of its sinfulness. This person sins willfully but doesn't really care. The person in the legal state comes under fear and an awareness of bondage to sin. He or she wants to stop sinning but cannot (Rom. 7). Finally, in the evangelical state one may still struggle against sin but this person is able not to sin.
Since Wesley likens the second state to being under law, the evangelical state is being under grace and being a child of God. He calls it at one point a "state of love" (IV.2).
So I infer that what Wesley means by evangelical here is something like "under the good news" or "under the gospel." The good news for him in this instance is that a person has been freed from the law and empowered by the Spirit to love and not sin.
I'm sure others could shed more light on what he meant. I did a quick search on the NNU Wesley site and found one other sermon in which Wesley used the adjective ("Spirit Bears Witness"). I noticed also that Arminius used the term in the 1600s. My first thought was that perhaps it was associated with Luther's idea of justification by faith as the essence of the good news?
There is much that could be studied here and no doubt it's been done. I am just not ready to trust what's been done. In any case, Wesley doesn't use the word "evangelical" anything close to the way we do today.
P.S. We can't fault Wesley for being a child of his age. For us today, he is a poor model of how to do exegesis. But that doesn't mean that his theology is wrong. We read Wesley for his theology, not for how to do inductive Bible study. There is a picture of truth in this sermon, even if it is not absolute or exactly what Paul was thinking.