'Ingenious' and 'Ingenuous': More Than a Typo
The adjectives ingenious and ingenuous differ by one letter, and if that’s not enough to confuse them, it doesn’t help that the differing letters are next to each other on the QWERTY keyboard. So naturally they get conflated pretty often, with one sometimes mis-typed in place of the other. But in other instances, people genuinely confuse the meanings of the words as well.
Ingenious means “having or showing an unusual aptitude for discovering, inventing, or contriving" or “marked by originality, resourcefulness, and cleverness in conception or execution.” More to the point, it describes people who come up with clever ideas or solutions or the ideas or solutions they come up with. The word derives via Middle English and Middle French from the Latin ingenium, which also gave us engine, a word that originally meant “ingenuity.”
A group of Kentucky middle schoolers have won a prestigious award for developing an ingenious device that lets first responders to safely collect hazardous needles left behind by opioid and other drug users.
— James Rogers, FoxNews.com, 16 May 2018
In ingenious one might hear the word genius, which we use for someone who possesses extraordinary intellect or has a strong aptitude for something (“she’s a genius at fixing computers”). Geniuses certainly might come up with ingenious ideas, but there’s no etymological relation between the words. Genius originally referred to an attendant spirit and derives from the Latin verb gignere (“to beget”).
Ingenuous means “showing innocent or childlike simplicity and candidness” or “lacking craft or subtlety.” It describes one who, like an innocent child, doesn't have the intent to deceive another.
Reinfeldt, who attended Boston College and trained at Commonwealth Shakespeare Company, brings a buoyant energy and an appealingly ingenuous demeanor to Casey, and the actor winningly handles the transition to the more worldly Georgia.
— Don Aucoin, The Boston Globe, 10 May 2018
For the first time I pitied this pretty girl with her bright hair and her Chucks, her long-limbed soda-colored legs, her ingenuous smile.
— Tamsyn Muir, The Magazine of Fantasy and Science Fiction, July/August 2015
On occasion one might see the two words juxtaposed and contrasted to highlight their distinction:
Permission to be wrong, wedded with a responsibility to be right, creates a powerful, civilizing tension. We are a species ingenious enough to project our intellect out across the universe, and ingenuous enough to feel awe at the spectacles the sky still offers at home.
— Jeffrey Kluger, Time.com, 15 Aug. 2017
One might also see in ingenuous the word ingenue, which nowadays might be used for a young female actress or performer but originally referred to a naïve girl or woman. Ingenuous sounds like it should be the opposite of genuine, until you realize that the in- prefix from Latin means “in-" or “within” and is not a negative prefix (as found in inconvenient). Ingenuous itself gets negated as disingenuous, which means “calculating” or “lacking in candor” and is actually slightly more common than its antonym.
One thing that complicates matters is that there was a time when ingenious and ingenuous were used synonymously, with most such use being restricted to the 16th through 18th centuries. Samuel Johnson’s 1755 dictionary did not recognize them as synonyms, and such usage fell out of favor by the end of the 18th century. So even if you feel like you're being ingenious by now using them in this creative and once historically-supported way, most people will probably see it as a mistake.