What is meant by “unwholesome words”?

Question

“Let no unwholesome word come out of your mouth, but if there is any good word for edification according to the need of the moment, say that, so that it will give grace to those who hear.” ‭‭Ephesians‬ ‭4:29‬

Is the the verse to justify against “cursing” & “swear words” for Christians? What did Paul mean in this context? What are unwholesome words defined as? Is there any historical interpretations here that Paul is using, that maybe don’t apply today?

Answer 1

Paul effectively answers this question of the meaning of "unwholesome talk", or, "corrupting talk", ESV, (Eph 4:29) a few verses later:

Eph 4:31 - Get rid of all bitterness, rage and anger, outcry and slander, along with every form of malice.

Eph 5:4 - Nor should there be obscenity, foolish talk, or crude joking, which are out of character, but rather thanksgiving.

Eph 5:6 - Let no one deceive you with empty words, for because of such things the wrath of God is coming on the sons of disobedience.

Benson comments on Eph 4:29 as follows:

The original expression, λογος σαπρος, is literally, rotten or putrid speech; that is, speech offensive to the hearers, or calculated to infect them with sin; and is in direct opposition to that which is seasoned with salt, and is recommended (Colossians 4:6) as tending to preserve persons from corruption. The apostle does not merely include in this expression obscene discourse of every kind, but also all flattery, calumny, railing, boasting, tale-bearing, backbiting, commendations of vice and impiety, profane jestings on religion, its ministers and professors, trifling conversation; and, indeed, all discourse that is not either about necessary business, or, as the next clause expresses it, is not good to the use of edifying — Calculated to instruct, direct, reprove, encourage, excite to duty, comfort, or in some way edify and minister grace to the hearers.

Answer 2

Basically, σαπρὸς means smelly or rotten. In the context it is words that tear down rather than edify. Thus, it encompasses a huge category.

σαπρός, ά, όν (...) decayed, rotten.

1. lit., of spoiled fish ...
2. fig. bad, evil, unwholesome ... -- Arndt, W., Gingrich, F. W., Danker, F. W., & Bauer, W. (1979). In A Greek-English lexicon of the New Testament and other early Christian literature : a translation and adaption of the fourth revised and augmented edition of Walter Bauer’s Griechisch-deutsches Worterbuch zu den Schrift en des Neuen Testaments und der ubrigen urchristlichen Literatur (p. 742). University of Chicago Press.

σαπρός, † σήπω

1. In basic meaning both words relate to the process of “decay.” a. σήπω act. “to cause to decay” ... b. σαπρός “rotting” ... Though what is lit. σαπρόν offends only sight or smell ...
2. In the LXX we find a. the act. σήπω once fig. “to destroy” ... b. “of poor quality” ...
3. ... decay ...
4. ... rotting ... Bauernfeind, O. (1964–). σαπρός, σήπω. In G. Kittel, G. W. Bromiley, & G. Friedrich (Eds.), Theological dictionary of the New Testament (electronic ed., Vol. 7, p. 94-97). Eerdmans.