Confusibles may look alike, or appear to have the same root, when in fact they don't. What they have in common is that they are commonly confused.

The confusion between flaunt and flout was mentioned here in the December issue, not for the first time, and, as you can see, not for the last. I was since told of someone on TV saying, "flaunt - flout - [shrug] whatever." At least he was aware that there is a difference, even if he didn't know what it is.
Such pairs (or groups) of words are sometimes called confusibles, and English abounds in them. They might look alike or sound alike, or appear to have the same root, when in fact they don't. What they have in common is that they are commonly confused, and it is sometimes difficult to find the reason.
One doesn't have to wait a long time to hear someone say, "I have a compunction to do this." The same person might say he felt compelled to do it, but would be unlikely to say he felt compuncted to do it, so why does he feel this compulsion to say compunction, which means a twinge of conscience?
Why would anyone say, "Any such interference would mitigate against the success of the plan," when he means militate? The words have some visual similarity, but reporters use militant dozens of times a day without ever saying mitigant. Have you ever heard about hundreds of banner-waving, sloganshouting anti-abortion mitigants storming a clinic? Anyway, proper usage mitigates confusion.
Once I was threatened with a libel action by a lawyer who charged, in writing, that I had "imputed his client's motives." I could only guess what he might have meant by that. I had, in fact, imputed certain motives to his client and then impugned those motives. I surmised that a lawyer who didn't know the difference between impute and impugn might easily be fended off with a burst of bafflegab. I was right.
Many people have difficulty with the verbs career and careen, and not without cause. The latter originally meant to lay a ship on its side for repairs. By extension, it came to be a transitive verb meaning toilet to one side, then, perhaps from side to side. It may be used to suggest a swaying or reeling progression. To career is to proceed at speed. usually through or over a course. A motorist indifferent to speed signs might career through a small town; if taken in drink, he might both career and careen through it. A skier might career through the slalom, although he could not do it without careening. One might careen through a career, but one cannot career through a careen. This is one of the trickier parts of confusibles, and it would be a blessing if those ignorant of the distinction would avoid using either word.
Here's a problem that doesn't bother speakers, but often confuses the journalists who report the speeches: a mediator in a labour dispute might say that he had made a discreet proposal to the union leader. Or did he say discrete? He might mean that he had quietly suggested something to the union man without letting management know. That would be discreet. Or perhaps he had made a proposal that was quite apart and distinct from whatever else was being negotiated, or one comprising several unrelated elements, in either of which cases the word would be discrete. A printed report using the inappropriate spelling could be misleading, no matter how one might pore (not pour) over it.
I used comprising is the preceding paragraph because of my high regard for the readers of Books in Canada. I would not dare do it in a lesser publication. Some authorities suggest avoiding comprise and using include, but there is a valid distinction: the whole comprises all the parts, but stay include some or all of them. Your dining suite, perhaps, Includes a table and a sideboard, but it comprises a table, a sideboard, eight chairs, and a thingummy. Comprises can be a useful word, but is not for people who eat in the kitchen.
I find it incredible that so many writers today think incredulous means difficult or impossible to believe, rather than indisposed to believe. In the 16th century, these words were sometimes used interchangeably by writers who should have known better, but is 400 years each word achieved a logical and useful distinction.
There are hundreds of confusibles. Perhaps their misuse by professional communicators can sometimes be blamed on heterophemy; more often it is the result of a lack of professionalism.