North Korean leader Kim Jong-un has confused a lot of English-speakers - though this time not about what he intends with his nuclear programme.
Responding to US President Donald Trump's bellicose warning to Pyongyang in his first speech to the United Nations on Tuesday, Mr Kim on Friday called Trump a "dotard" - at least in a translation by the state news agency KCNA.
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The obscure word is old - late Middle English, or around the 14th century - and means senile old person, someone in their dotage.
Although Shakespeare and Tolkien used it, the word is barely heard these days and Mr Kim's statement caused a Twitter storm of questions to Merriam-Webster dictionary about its meaning, while searches on Google also increased.
Merriam-Webster responded with a tweet, defining dotard as "a person in his or her dotage", which is "a state or period of senile decay marked by decline of mental poise and alertness", which quickly became the top trending post on Twitter on Friday, with more than 7400 retweets and 13,000 likes.
There were more than 100,000 mentions of the hashtag #dotard and 189,000 mentions of the word on Twitter on Friday, according to international social media analytics firm Talkwalker. On Google's Ngram Viewer, which tracks the popularity of words over time, "dotard" was a word that peaked in the 18th century.
Many social media users also took to Twitter to deliver their best jokes.
"By making people look up the word #dotard, Kim Jong-un has done more for American education than Betsy DeVos," wrote one user. Ms DeVos is the US Secretary of Education.
Other Twitter influencers did not find the insult amusing.
"This hashtag is a disgrace: #DotardTrump," tweeted LoConservative founder Kassy Dillon. "Whether you like him or not, Trump is your president & Kim Jong Un is a dictator & a murderer."
And novelist Elnathan John said: "Am I the only one who doesn't find this Trump-Jong Un war dance funny? Why are we all giggling at these two men who CAN destroy us? #dotard."