When he was told earlier this year not to like Twitter, the USA president is yet to its own commands and tweets (very) regularly on all possible subjects of its foreign policy to the supposed mediocrity of his opponent.
Was it tweetus incompletus?
It's unclear what the commander in chief was trying to say. Hours later, he deleted the tweet and challenged his followers to figure out its true meaning. But none of those sound right ("Despite the constant negative press, Coven is the best season of American Horror Story"?). "Enjoy!" he tweeted, in an unusual display of self-deprecating humour.
Even a misspelling of covfefe started trending: "cofveve", with the "v" and the "f's" reversed.
Perhaps it was meant as a follow-up to his previous tweet, in which he retweeted a Fox and Friends tweet citing an unnamed source who said, "Jared Kushner didn't suggest Russian communications channel in meeting". Silicon Valley executive Andrew Crow went as far to change his last name on Twitter to "Covfefe".
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Comedian Jimmy Kimmel tweeted, "what makes me saddest is that I know I'll never write anything funnier than #covfefe".
A California man reportedly registered covfefe as his license plate.
Whoever is managing Merriam-Webster's Twitter account deserves praise for remaining patient at such a time. Moreover, during the trip the president was accompanied by his wife and was rarely alone with his phone - unlike his frequent solitary nights at the White House.
Then, around 0945 GMT, more than five hours after it was posted, the mysterious tweet vanished.