Charles Hodge on Ephesians 5:4

V. 4. Neither filthiness. The word αἰσχρότης, is not simply obscenity, but whatever is morally hateful. The adjective αἰσχρος means deformed, revolting, what excites disgust, physical or moral. It is the opposite of καλός, which means both beautiful and good; and hence τὸ καλόν καὶ τὸ αἰσχρόν, means virtue and vice, The substantive is equally comprehensive, and includes whatever is vile or disgusting in speech or conduct. Lesser evils are expressed by the words μωρολογία and εὐτραπελία, foolish talking and jesting. The former means such talk as is characteristic of fools, i. e. frivolous and senseless. The latter, according to its etymology and early usage, means urbanity, politeness. Naturally enough however the word came to have a bad sense, as the adjective εὐτράπελος, what turns easily, as the wind, when applied to language or speech, means not only adroit, skilful, agreeable, witty, but also flippant, satirical, scurrilous. Hence the substantive is used for jesting and scurrility. The former sense is best suited to this passage, because it is connected with foolish talking, and because the apostle says of both simply that they are not convenient, not becoming or suitable. This is too mild a form of expression to be used either of αἰσχρότης (filthiness) or of εὐτραπελία in the worse sense of those terms. Paul says, these things (foolish talking and jesting) do not become Christians; οὐκ ἀνήκοντα, what does not pertain to any one, or, to his office. Foolish talking and jesting are not the ways in which Christian cheerfulness should express itself, but rather giving of thanks. Religion is the source of joy and gladness, but its joy is expressed in a religious way, in thanksgiving and praise.