Etymology: An Overview
The term "etymology" may refer to the branch of linguistics that deals with word formations (origins): etymologists trace a signifier's development through time. These students of language primarily want to know the diachronic aspects of a word as opposed to its synchronic elements. However, this fact does not mean that etymologists necessarily fail to study a word's synchronic aspects. But in etymological studies, diachrony naturally takes precedence.
Yet linguists generally recognize that language is not static--it changes over time and morphic substances (words) thus acquire new meanings as they come to signify different concepts or stand for various referents. For instance, the English word "salary" derives from the Latin salarium. The Latin term once referred to "money allowed to Roman soldiers for the purchase of salt" (The Concise Oxford Dictionary of English Etymology). Today, the word signifies a form of pay (a stipend) without denoting what salarium once meant.
We can make the same claim for the Greek word μῦθος. At one time, μῦθος simply denoted a "word,"speech," "tale," "story" without any necessary connotations of falsehood (cf. Classical Mythology by Mark P.O. Morford and Robert J. Lenardon). In Homer, μῦθος clearly has reference to a truthful account (a trustworthy report) of eagerly anticipated details. By the first century BCE-CE, however, μῦθος starts to be employed pejoratively by both Philo of Alexandria and the GNT writers (2 Peter 1:16ff). We also note a semantic shift vis-à-vis other Greek words such as ἁμαρτία and μορφή. It should not surprise us, therefore, if ἁρπαγμός also underwent change per its lexicality.
At this point, I would encourage the reader not to conclude that etymology (the study of primary word forms) is never helpful. Such thinking is far from accurate. Besides, understanding how compound signifiers work can be useful when learning Greek vocabulary, and etymology also comes in handy when one is trying to decipher an unfamiliar English word. The person who knows the etymology of adjectives like "doxastic," "alethic," "logocentric" and "heliocentric" can easily decode such esoteric speech; this blog post is thus not meant to downgrade all types of etymologizing. But one must use caution when undertaking word studies. Etymology can be a blessing if used aright--it can also be a maleficent tool when employed otherwise.
For instance, D.A. Carson gives some pertinent examples of what he calls "the root fallacy" on pp. 28-33 of his Exegetical Fallacies (Second Edition). Some common instances of the root fallacy are popular explanations that we find for the etymological derivation of the words ἀπόστολος, ὑπηρέτης, ἀγαπάω, and I will add, ἐκκλησία.
One often hears that ἐκκλησία means "called out ones." That is an explanation given based on the word's etymology, but it's not what ἐκκλησία signifies in the GNT, however. The word denotes an "assembly" or "congregation." It does not refer to those called out per se, nor does the word signify a building. Etymology and/or semantic anachronism can deceive us in this case, if we rely on them too much.