The internet is full of confident people who do not know what they are talking about. The latest example: a conviction spreading in right-leaning social media communities that a garbled tweet by the president — he wrote “covfefe” — was not a late-night typo but was instead Mr. Trump sending a message to the world in Arabic.

“Covfefe,” these people on the internet insist, is Arabic for “I will stand up.” That is not even close to true. We asked Ali Adeeb Alnaemi, a professor of Arabic at New York University, what he thought of this translation, which has been falsely spread online by anonymous Reddit users with screen names like “PepeTheRacistFrog.”