Decorous Got Its Start With Etiquette

The current meaning of decorous dates from the mid-17th century. One of the word's earliest recorded uses appears in a book titled The Rules of Civility (1673): "It is not decorous to look in the Glass, to comb, brush, or do any thing of that nature to ourselves, whilst the said person be in the Room." Decorous for a time had another meaning as well—"fitting or appropriate"—but that now-obsolete sense seems to have existed for only a few decades in the 17th century. Decorous derives from the Latin word decorus, an adjective created from the noun decor, meaning "beauty" or "grace." Decor is akin to the Latin verb decēre ("to be fitting"), which is the source of our adjective decent. It is only fitting, then, that decent can be a synonym of decorous.