Early in the history of the Confessional Lutheran church, Lutherans were already called "evangelicals." This was their preferred label, meant to distinguish them from both the Roman papacy and the later, more radical reformers like Ulrick Zwingli and John Calvin.
Many Lutheran Churches still retain the adjective "evangelical" in their names, and the reason is often the same as it was for the early Lutherans: to distinguish our churches from the Roman Catholic Church on one hand and the more radically reformed churches hailing from teachers like Ulrick Zwingli, John Calvin, John Wesley, and the like. From the Lutheran point of view, the adjective "evangelical" is still a meaningful distinction, because only the Confessional Lutheran church consistently teaches that we are saved by God's work alone, from start to finish. That message is the essence of the biblical evangel, the gospel or "good news" concerning Jesus Christ.
Since the 19th Century in America, a tradition of Christian teaching has arisen and dominated the American landscape rooted in the teachings of John Calvin, and further inspired by teachers like John Wesley and Charles Finney. This teaching contradicts Confessional Lutheran teaching, but has since become commonly known as "Evangelicalism."
Instead of emphasizing that we are saved by God's work alone, the "new evangelicals" emphasize "conformity to the basic tenets of the faith and a missionary outreach of compassion and urgency" (wording from this online source). While this emphasis would not necessarily contradict the Gospel, many evangelical teachers stress that their hearers must do something in order to receive the benefits of God's mercy, which are forgiveness of sins and eternal life. From the Lutheran point of view, this teaching has the same basic problem as the Roman Catholic teaching: salvation depends upon us, at least in part.
Many Confessional Lutherans today still call themselves "evangelical" Lutherans, with the understanding that we teach the unqualified, undiluted Gospel of salvation by God's grace alone, through faith alone, without any dependency upon the works or efforts of sinful human beings. (Ephesians 2:8-9) That's what Bethany and Concordia congregations mean when we call ourselves "evangelical" Lutheran congregations.