Vine's Expository Dictionary of NT Words 
an adjective (cp. aitia, a cause), denotes "that which causes something." This and No. 2 are both translated "author" in Hebrews. Aitios, in Hebrews 5:9 , describes Christ as the "Author of eternal salvation unto all them that obey Him," signifying that Christ, exalted and glorified as our High Priest, on the ground of His finished work on earth, has become the personal mediating cause (RV, margin) of eternal salvation. It is difficult to find an adequate English equivalent to express the meaning here. Christ is not the merely formal cause of our salvation. He is the concrete and active cause of it. He has not merely caused or effected it, He is, as His name, "Jesus," implies, our salvation itself, Luke 2:30; 3:6 .
translated "Prince" in Acts 3:15 (marg., "Author") and Acts 5:31 , but "Author" in Hebrews 2:10 , RV, "Captain," RV marg., and AV, and "Author" in Hebrews 12:2 , primarily signifies "one who takes a lead in, or provides the first occasion of, anything." In the Sept. it is used of the chief of a tribe or family, Numbers 13:2 (RV, prince); of the "heads" of the children of Israel, Numbers 13:3; a captain of the whole people, Numbers 14:4; in Micah 1:13 , of Lachish as the leader of the sin of the daughter of Sion: there, as in Hebrews 2:10 , the word suggest a combination of the meaning of leader with that of the source from whence a thing proceeds. That Christ is the Prince of life signifies, as Chrysostom says, that "the life He had was not from another; the Prince or Author of life must be He who has life from Himself." But the word does not necessarily combine the idea of the source or originating cause with that of leader. In Hebrews 12:2 where Christ is called the "Author and Perfecter of faith," He is represented as the one who takes precedence in faith and is thus the perfect exemplar of it. The pronoun "our" does not correspond to anything in the original, and may well be omitted. Christ in the days of His flesh trod undeviatingly the path of faith, and as the Perfecter has brought it to a perfect end in His own person. Thus He is the leader of all others who tread that path. See Prince.
Morrish Bible Dictionary 
1. ἀρχηγός,'beginner, leader.' It is 'prince' in Acts 3:15 ('author' in the margin), the Lord Jesus is the originator of life. In Hebrews 12:2 , the Lord Jesus is the 'leader ' and completer of faith: He began and finished the whole course. In Hebrews 2:10 it is 'captain ' in the A.V., He was 'leader' of their salvation through suffering
2. αἴτιος, 'cause,' 'occasion.' The Lord Jesus became the author of eternal salvation.' Hebrews 5:9 .
King James Dictionary 
AU'THOR, n. L. auctor. The Latin word is from the root of augeo, to increase, or cause to enlarge. The primary sense is one who brings or causes to come forth.
1. One who produces, creates, or brings into being as, God is the author of the Universe. 2. The beginner, former, or first mover of any thing hence, the efficient cause of a thing. It is appropriately applied to one who composes or writes a book, or original work, and in a more general sense, to one whose occupation is to compose and write books opposed to compiler or translator.
AU'THOR, To occasion to effect. Not used.
Webster's Dictionary 
(1): (n.) The beginner, former, or first mover of anything; hence, the efficient cause of a thing; a creator; an originator.
(2): (n.) One who composes or writes a book; a composer, as distinguished from an editor, translator, or compiler.
(3): (n.) The editor of a periodical.
(4): (n.) An informant.
(5): (v. t.) To occasion; to originate.
(6): (v. t.) To tell; to say; to declare.
Wilson's Dictionary of Bible Types 
Hebrews 5:9 (a) Christ designed, planned and executed salvation "by Himself." He presents this salvation as a gift to all who will receive Him. All other forms of "salvation" are an invention of some man or some woman, and only lead to the outer dark.
Hebrews 12:2 (a) CHRIST produces faith in the heart as we look upon Him, think about Him, read about Him, and talk with Him. His very person causes us to believe in Him fully, and to trust in Him implicitly.
International Standard Bible Encyclopedia 
ô´thẽr : This word is used to translate two Greek words: (1) αἴτιος , aı́tios , literally, "cause," hence, "author." Hebrews 5:9 , He "became the author of eternal salvation." (2) ἀρχηγός , archēgós = literally, "chief leader," "prince," "captain"; then author, originator. It is rendered "author" in the following passages: ( a ) Hebrews 12:2 , "looking unto Jesus, the author [King James Version, Revised Version and finisher [Revised Version, "perfecter" of our faith." But here it seems better to take archēgos in its primary sense, "leader" (Revised Version margin "captain"), rather than in its secondary sense "author." The meaning is, not that He is the originator of faith in us, but that He Himself is the pioneer in the life of faith. He is first in the company of the faithful (compare references to His "faithfulness," Hebrews 2:17; Hebrews 3:2 , Hebrews 3:5 , Hebrews 3:6 ), far surpassing in His fidelity even the Old Testament saints mentioned in chapter 11; and therefore we are to look to Him as our perfect pattern of faith. Faith has not only Christ for its object, but Christ for its supreme example. So Bengel, Bleek, B. Weiss, Alford, A. B. Davidson, Grimm-Thayer. Others, however, take the word in the sense of "author." ( b ) Hebrews 2:10 , "to make the author [King James Version, "captain" of their salvation perfect through sufferings." Here the idea of Christ as originator or author of our salvation is present (compare the passage Hebrews 5:9 , where however a different word is used; see above). But here again the original meaning of "leader" is not to be lost sight of. He, being the first possessor of salvation, becomes the author of it for others. "The idea that the Son goes before the saved in the same path ought perhaps to be retained" (Davidson). Compare Hebrews 6:20 , where Jesus is said to be our "forerunner." (c) Acts 3:15 , King James Version margin and the Revised Version margin have "author," where text has "prince." Here again it is possible that the two ideas are present.