What’s the difference between ingenious and ingenuous, and are they even related? If you believe that despite their seeming disparity in meaning, these words belong to the same genus, you’re a genius — and you therefore probably know as well that those terms with the common element gen share their origin with the first pair of words.
Ingenious, ingenuous, and several other words and their variations are derived ultimately from the Latin verb gignere, which means “to produce.” One of that term’s descendants is engine, which traces from ingenium, meaning “talent.” Originally, engine meant “trick or device,” but it later came to be applied to machines used in warfare and then to mechanisms in general. Gin, an abbreviation of the French form engin, eventually referred specifically to a device that separates cotton from the cotton plant’s seeds. (The name of the alcoholic beverage gin and that of the card game gin rummy are corruptions of the place name Geneva and are unrelated.)
Genus, meaning “a class or kind,” and general, with the same basic meaning but best known for other connotations and in various forms, are ancient kin of these other words including the element gen. So is genius, which first referred to a guardian spirit but came to apply to innate talent. Two other closely related words are genie, from the French form of genius (which later was associated with the similar-sounding but unrelated Arabic word djinn to refer, in French and later English translations, to a spirit or force in Arabian mythology and folklore) and genial, also descended from genius but now meaning “friendly,” as well as congenial (“pleasant, harmonious”).
Ingenious developed a sense of “clever” through its predecessor ingenium. Ingenuous, however, took a different route, evolving in sense from “high-minded” to “straightforward” to “innocent.” The feminine form in French, ingénu, altered in English to ingenue, came to refer to a stage character defined by her artless simplicity. The term was extended to apply to a young, innocent female lead character in live and recorded performances and in literature (and, occasionally, to such a person in general).