Watson's Biblical & Theological Dictionary 
the inspired authors of the Gospels. The word is derived from the Greek, ευαγτελιον , formed of ευ , bene, "well," and αγτελος , angel, messenger. The name of evangelists is said by some to have been given in the ancient church to such as preached the Gospel without being attached to any particular church, being either commissioned by the Apostles to instruct the nations, or, of their own accord, abandoning every worldly attachment, consecrated themselves to the sacred office of preaching the Gospel. In which sense these interpreters think it is that St. Philip, who was one of the seven deacons, is called "the evangelist" in Acts 21:8; and that St. Paul, writing to Timothy, bids him do the work of an evangelist, 2 Timothy 4:5 . It is, however, to be remarked, that the office in which the evangelists chiefly present themselves to our notice in the New Testament, is that of assistants to the Apostles; or, as they might be termed, vice apostles, who acted under their authority and direction. As they were directed to ordain pastors or bishops in the churches, but had no authority given them to ordain successors to themselves in their particular office as evangelists, whatever it might be, they must be considered as but temporary officers in the church, like the Apostles and prophets. The term evangelist is, at present, confined to the writers of the four Gospels.
Kitto's Popular Cyclopedia of Biblial Literature 
This term is applied in the New Testament to a certain class of Christian teachers who were not fixed to any particular spot, but traveled either independently, or under the direction of one or other of the Apostles, for the purpose of propagating the Gospel. Philip, one of the seven deacons, is termed the Evangelist . St. Paul exhorts Timothy 'to do the work of an Evangelist' and though this name is not given to Titus, the injunctions addressed to him, and the services he rendered, are so similar as to render the propriety of applying it to him unquestionable. In the Epistle to the Ephesians the Evangelists are expressly distinguished from the pastors and teachers. The chief points of difference appear to be that the former were itinerant, the latter stationary; the former were employed in introducing the Gospel where it was before unknown; the business of the latter was to confirm and instruct the converts statedly and permanently.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
In the British census of 1851 four congregations returned themselves as worshipping under this name, probably to avoid being identified with any sect.